MySQL Information Schema

MySQL Information Schema
Abstract
This is the MySQL Information Schema extract from the MySQL 5.6 Reference Manual.
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Document generated on: 2018-02-16 (revision: 56032)
Table of Contents
Preface and Legal Notices .................................................................................................................. v
1 INFORMATION_SCHEMA Tables .................................................................................................... 1
2 The INFORMATION_SCHEMA SCHEMATA Table ........................................................................... 5
3 The INFORMATION_SCHEMA TABLES Table ................................................................................. 7
4 The INFORMATION_SCHEMA COLUMNS Table ............................................................................. 9
5 The INFORMATION_SCHEMA STATISTICS Table ......................................................................... 11
6 The INFORMATION_SCHEMA USER_PRIVILEGES Table ............................................................. 13
7 The INFORMATION_SCHEMA SCHEMA_PRIVILEGES Table ........................................................ 15
8 The INFORMATION_SCHEMA TABLE_PRIVILEGES Table ............................................................ 17
9 The INFORMATION_SCHEMA COLUMN_PRIVILEGES Table ........................................................ 19
10 The INFORMATION_SCHEMA CHARACTER_SETS Table ........................................................... 21
11 The INFORMATION_SCHEMA COLLATIONS Table ..................................................................... 23
12 The INFORMATION_SCHEMA COLLATION_CHARACTER_SET_APPLICABILITY Table ............... 25
13 The INFORMATION_SCHEMA TABLE_CONSTRAINTS Table ...................................................... 27
14 The INFORMATION_SCHEMA KEY_COLUMN_USAGE Table ...................................................... 29
15 The INFORMATION_SCHEMA ROUTINES Table ......................................................................... 31
16 The INFORMATION_SCHEMA VIEWS Table ............................................................................... 33
17 The INFORMATION_SCHEMA TRIGGERS Table ......................................................................... 35
18 The INFORMATION_SCHEMA PLUGINS Table ........................................................................... 37
19 The INFORMATION_SCHEMA ENGINES Table ........................................................................... 39
20 The INFORMATION_SCHEMA PARTITIONS Table ...................................................................... 41
21 The INFORMATION_SCHEMA EVENTS Table ............................................................................. 45
22 The INFORMATION_SCHEMA FILES Table ................................................................................. 49
23 The INFORMATION_SCHEMA PROCESSLIST Table ................................................................... 55
24 The INFORMATION_SCHEMA REFERENTIAL_CONSTRAINTS Table .......................................... 57
25 The INFORMATION_SCHEMA GLOBAL_STATUS and SESSION_STATUS Tables ....................... 59
26 The INFORMATION_SCHEMA GLOBAL_VARIABLES and SESSION_VARIABLES Tables ............. 61
27 Extensions to SHOW Statements ................................................................................................. 63
28 MySQL 5.6 FAQ: INFORMATION_SCHEMA ................................................................................ 65
iii
iv
Preface and Legal Notices
This is the MySQL Information Schema extract from the MySQL 5.6 Reference Manual.
Legal Notices
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v
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vi
Chapter 1 INFORMATION_SCHEMA Tables
INFORMATION_SCHEMA provides access to database metadata, information about the MySQL server such
as the name of a database or table, the data type of a column, or access privileges. Other terms that are
sometimes used for this information are data dictionary and system catalog.
INFORMATION_SCHEMA Usage Notes
INFORMATION_SCHEMA is a database within each MySQL instance, the place that stores information
about all the other databases that the MySQL server maintains. The INFORMATION_SCHEMA database
contains several read-only tables. They are actually views, not base tables, so there are no files associated
with them, and you cannot set triggers on them. Also, there is no database directory with that name.
Although you can select INFORMATION_SCHEMA as the default database with a USE statement, you can
only read the contents of tables, not perform INSERT, UPDATE, or DELETE operations on them.
Example
Here is an example of a statement that retrieves information from INFORMATION_SCHEMA:
mysql> SELECT table_name, table_type, engine
FROM information_schema.tables
WHERE table_schema = 'db5'
ORDER BY table_name;
+------------+------------+--------+
| table_name | table_type | engine |
+------------+------------+--------+
| fk
| BASE TABLE | InnoDB |
| fk2
| BASE TABLE | InnoDB |
| goto
| BASE TABLE | MyISAM |
| into
| BASE TABLE | MyISAM |
| k
| BASE TABLE | MyISAM |
| kurs
| BASE TABLE | MyISAM |
| loop
| BASE TABLE | MyISAM |
| pk
| BASE TABLE | InnoDB |
| t
| BASE TABLE | MyISAM |
| t2
| BASE TABLE | MyISAM |
| t3
| BASE TABLE | MyISAM |
| t7
| BASE TABLE | MyISAM |
| tables
| BASE TABLE | MyISAM |
| v
| VIEW
| NULL
|
| v2
| VIEW
| NULL
|
| v3
| VIEW
| NULL
|
| v56
| VIEW
| NULL
|
+------------+------------+--------+
17 rows in set (0.01 sec)
Explanation: The statement requests a list of all the tables in database db5, showing just three pieces of
information: the name of the table, its type, and its storage engine.
Character Set Considerations
The definition for character columns (for example, TABLES.TABLE_NAME) is generally VARCHAR(N)
CHARACTER SET utf8 where N is at least 64. MySQL uses the default collation for this character set
(utf8_general_ci) for all searches, sorts, comparisons, and other string operations on such columns.
Because some MySQL objects are represented as files, searches in INFORMATION_SCHEMA string
columns can be affected by file system case sensitivity. For more information, see Using Collation in
INFORMATION_SCHEMA Searches.
1
INFORMATION_SCHEMA as Alternative to SHOW Statements
INFORMATION_SCHEMA as Alternative to SHOW Statements
The SELECT ... FROM INFORMATION_SCHEMA statement is intended as a more consistent way to
provide access to the information provided by the various SHOW statements that MySQL supports (SHOW
DATABASES, SHOW TABLES, and so forth). Using SELECT has these advantages, compared to SHOW:
• It conforms to Codd's rules, because all access is done on tables.
• You can use the familiar syntax of the SELECT statement, and only need to learn some table and column
names.
• The implementor need not worry about adding keywords.
• You can filter, sort, concatenate, and transform the results from INFORMATION_SCHEMA queries into
whatever format your application needs, such as a data structure or a text representation to parse.
• This technique is more interoperable with other database systems. For example, Oracle Database users
are familiar with querying tables in the Oracle data dictionary.
Because SHOW is familiar and widely used, the SHOW statements remain as an alternative. In fact, along
with the implementation of INFORMATION_SCHEMA, there are enhancements to SHOW as described in
Chapter 27, Extensions to SHOW Statements.
Privileges
Each MySQL user has the right to access these tables, but can see only the rows in the tables that
correspond to objects for which the user has the proper access privileges. In some cases (for example,
the ROUTINE_DEFINITION column in the INFORMATION_SCHEMA.ROUTINES table), users who have
insufficient privileges see NULL. These restrictions do not apply for InnoDB tables; you can see them with
only the PROCESS privilege.
The same privileges apply to selecting information from INFORMATION_SCHEMA and viewing the same
information through SHOW statements. In either case, you must have some privilege on an object to see
information about it.
Performance Considerations
INFORMATION_SCHEMA queries that search for information from more than one database might take
a long time and impact performance. To check the efficiency of a query, you can use EXPLAIN. For
information about using EXPLAIN output to tune INFORMATION_SCHEMA queries, see Optimizing
INFORMATION_SCHEMA Queries.
Standards Considerations
The implementation for the INFORMATION_SCHEMA table structures in MySQL follows the ANSI/ISO
SQL:2003 standard Part 11 Schemata. Our intent is approximate compliance with SQL:2003 core feature
F021 Basic information schema.
Users of SQL Server 2000 (which also follows the standard) may notice a strong similarity. However,
MySQL has omitted many columns that are not relevant for our implementation, and added columns that
are MySQL-specific. One such column is the ENGINE column in the INFORMATION_SCHEMA.TABLES
table.
Although other DBMSs use a variety of names, like syscat or system, the standard name is
INFORMATION_SCHEMA.
2
Conventions in the INFORMATION_SCHEMA Reference Sections
To avoid using any name that is reserved in the standard or in DB2, SQL Server, or Oracle, we changed
the names of some columns marked “MySQL extension”. (For example, we changed COLLATION to
TABLE_COLLATION in the TABLES table.) See the list of reserved words near the end of this article:
https://web.archive.org/web/20070428032454/http://www.dbazine.com/db2/db2-disarticles/gulutzan5.
Conventions in the INFORMATION_SCHEMA Reference Sections
The following sections describe each of the tables and columns in INFORMATION_SCHEMA. For each
column, there are three pieces of information:
• “INFORMATION_SCHEMA Name” indicates the name for the column in the INFORMATION_SCHEMA table.
This corresponds to the standard SQL name unless the “Remarks” field says “MySQL extension.”
• “SHOW Name” indicates the equivalent field name in the closest SHOW statement, if there is one.
• “Remarks” provides additional information where applicable. If this field is NULL, it means that the value
of the column is always NULL. If this field says “MySQL extension,” the column is a MySQL extension to
standard SQL.
Many sections indicate what SHOW statement is equivalent to a SELECT that retrieves information from
INFORMATION_SCHEMA. For SHOW statements that display information for the default database if you omit
a FROM db_name clause, you can often select information for the default database by adding an AND
TABLE_SCHEMA = SCHEMA() condition to the WHERE clause of a query that retrieves information from an
INFORMATION_SCHEMA table.
Related Information
These sections discuss additional INFORMATION_SCHEMA-related topics:
• information about INFORMATION_SCHEMA tables specific to the InnoDB storage engine: InnoDB
INFORMATION_SCHEMA Tables
• information about INFORMATION_SCHEMA tables specific to the NDB storage engine (NDB Cluster): NDB
Cluster INFORMATION_SCHEMA Tables
• information about INFORMATION_SCHEMA tables specific to the thread pool plugin: Thread Pool
INFORMATION_SCHEMA Tables
• Answers to questions that are often asked concerning the INFORMATION_SCHEMA database:
Chapter 28, MySQL 5.6 FAQ: INFORMATION_SCHEMA
• INFORMATION_SCHEMA queries and the optimizer: Optimizing INFORMATION_SCHEMA Queries
• The effect of collation on INFORMATION_SCHEMA comparisons: Using Collation in
INFORMATION_SCHEMA Searches
3
4
Chapter 2 The INFORMATION_SCHEMA SCHEMATA Table
A schema is a database, so the SCHEMATA table provides information about databases.
INFORMATION_SCHEMA Name
SHOW Name
CATALOG_NAME
SCHEMA_NAME
Remarks
def
Database
DEFAULT_CHARACTER_SET_NAME
DEFAULT_COLLATION_NAME
SQL_PATH
NULL
The following statements are equivalent:
SELECT SCHEMA_NAME AS `Database`
FROM INFORMATION_SCHEMA.SCHEMATA
[WHERE SCHEMA_NAME LIKE 'wild']
SHOW DATABASES
[LIKE 'wild']
5
6
Chapter 3 The INFORMATION_SCHEMA TABLES Table
The TABLES table provides information about tables in databases.
INFORMATION_SCHEMA Name
SHOW Name
TABLE_CATALOG
Remarks
def
TABLE_SCHEMA
Table_...
TABLE_NAME
Table_...
TABLE_TYPE
ENGINE
Engine
MySQL extension
VERSION
Version
The version number of the
table's .frm file, MySQL
extension
ROW_FORMAT
Row_format
MySQL extension
TABLE_ROWS
Rows
MySQL extension
AVG_ROW_LENGTH
Avg_row_length
MySQL extension
DATA_LENGTH
Data_length
MySQL extension
MAX_DATA_LENGTH
Max_data_length
MySQL extension
INDEX_LENGTH
Index_length
MySQL extension
DATA_FREE
Data_free
MySQL extension
AUTO_INCREMENT
Auto_increment
MySQL extension
CREATE_TIME
Create_time
MySQL extension
UPDATE_TIME
Update_time
MySQL extension
CHECK_TIME
Check_time
MySQL extension
TABLE_COLLATION
Collation
MySQL extension
CHECKSUM
Checksum
MySQL extension
CREATE_OPTIONS
Create_options
MySQL extension
TABLE_COMMENT
Comment
MySQL extension
INDEX_COMMENT
Index_comment
MySQL extension
Notes:
• Refer to SHOW TABLE STATUS for field descriptions.
• TABLE_SCHEMA and TABLE_NAME are a single field in a SHOW display, for example Table_in_db1.
• TABLE_TYPE should be BASE TABLE or VIEW. The TABLES table does not list TEMPORARY tables.
• For partitioned tables, the ENGINE column shows the name of the storage engine used by all partitions.
(Previously, this column showed PARTITION for such tables.)
• The TABLE_ROWS column is NULL if the table is in the INFORMATION_SCHEMA database.
For InnoDB tables, the row count is only a rough estimate used in SQL optimization. (This is also true if
the InnoDB table is partitioned.)
• The DATA_FREE column shows the free space in bytes for InnoDB tables.
7
• Prior to MySQL 5.6.25, for partitioned InnoDB tables, the CREATE_TIME column showed NULL.
This column shows the correct table creation time for such tables in MySQL 5.6.25 and later. (Bug
#17299181, Bug #69990)
For partitioned InnoDB tables, the UPDATE_TIME and CHECK_TIME columns are always NULL.
• We have nothing for the table's default character set. TABLE_COLLATION is close, because collation
names begin with a character set name.
• The CREATE_OPTIONS column shows partitioned if the table is partitioned.
The following statements are equivalent:
SELECT table_name FROM INFORMATION_SCHEMA.TABLES
WHERE table_schema = 'db_name'
[AND table_name LIKE 'wild']
SHOW TABLES
FROM db_name
[LIKE 'wild']
8
Chapter 4 The INFORMATION_SCHEMA COLUMNS Table
The COLUMNS table provides information about columns in tables.
INFORMATION_SCHEMA Name
SHOW Name
TABLE_CATALOG
Remarks
def
TABLE_SCHEMA
TABLE_NAME
COLUMN_NAME
Field
see notes
ORDINAL_POSITION
COLUMN_DEFAULT
Default
IS_NULLABLE
Null
DATA_TYPE
Type
CHARACTER_MAXIMUM_LENGTH
Type
CHARACTER_OCTET_LENGTH
NUMERIC_PRECISION
Type
NUMERIC_SCALE
Type
DATETIME_PRECISION
Type
CHARACTER_SET_NAME
COLLATION_NAME
Collation
COLUMN_TYPE
Type
MySQL extension
COLUMN_KEY
Key
MySQL extension
EXTRA
Extra
MySQL extension
PRIVILEGES
Privileges
MySQL extension
COLUMN_COMMENT
Comment
MySQL extension
Notes:
• In SHOW, the Type display includes values from several different COLUMNS columns.
• ORDINAL_POSITION is necessary because you might want to say ORDER BY ORDINAL_POSITION.
Unlike SHOW, SELECT does not have automatic ordering.
• CHARACTER_OCTET_LENGTH should be the same as CHARACTER_MAXIMUM_LENGTH, except for
multibyte character sets.
• CHARACTER_SET_NAME can be derived from Collation. For example, if you say SHOW FULL
COLUMNS FROM t, and you see in the Collation column a value of latin1_swedish_ci, the
character set is what is before the first underscore: latin1.
• DATETIME_PRECISION was added in MySQL 5.6.4.
The following statements are nearly equivalent:
SELECT COLUMN_NAME, DATA_TYPE, IS_NULLABLE, COLUMN_DEFAULT
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = 'tbl_name'
9
[AND table_schema = 'db_name']
[AND column_name LIKE 'wild']
SHOW COLUMNS
FROM tbl_name
[FROM db_name]
[LIKE 'wild']
10
Chapter 5 The INFORMATION_SCHEMA STATISTICS Table
The STATISTICS table provides information about table indexes.
INFORMATION_SCHEMA Name
SHOW Name
Remarks
TABLE_CATALOG
def
TABLE_SCHEMA
= Database
TABLE_NAME
Table
NON_UNIQUE
Non_unique
= Database
INDEX_SCHEMA
INDEX_NAME
Key_name
SEQ_IN_INDEX
Seq_in_index
COLUMN_NAME
Column_name
COLLATION
Collation
CARDINALITY
Cardinality
SUB_PART
Sub_part
MySQL extension
PACKED
Packed
MySQL extension
NULLABLE
Null
MySQL extension
INDEX_TYPE
Index_type
MySQL extension
COMMENT
Comment
MySQL extension
Notes:
• There is no standard table for indexes. The preceding list is similar to what SQL Server 2000 returns for
sp_statistics, except that we replaced the name QUALIFIER with CATALOG and we replaced the
name OWNER with SCHEMA.
Clearly, the preceding table and the output from SHOW INDEX are derived from the same parent. So the
correlation is already close.
The following statements are equivalent:
SELECT * FROM INFORMATION_SCHEMA.STATISTICS
WHERE table_name = 'tbl_name'
AND table_schema = 'db_name'
SHOW INDEX
FROM tbl_name
FROM db_name
11
12
Chapter 6 The INFORMATION_SCHEMA USER_PRIVILEGES
Table
The USER_PRIVILEGES table provides information about global privileges. This information comes from
the mysql.user grant table.
INFORMATION_SCHEMA Name
SHOW Name
Remarks
GRANTEE
'user_name'@'host_name'
value, MySQL extension
TABLE_CATALOG
def, MySQL extension
PRIVILEGE_TYPE
MySQL extension
IS_GRANTABLE
MySQL extension
Notes:
• This is a nonstandard table. It takes its values from the mysql.user table.
13
14
Chapter 7 The INFORMATION_SCHEMA
SCHEMA_PRIVILEGES Table
The SCHEMA_PRIVILEGES table provides information about schema (database) privileges. This
information comes from the mysql.db grant table.
INFORMATION_SCHEMA Name
SHOW Name
Remarks
GRANTEE
'user_name'@'host_name'
value, MySQL extension
TABLE_CATALOG
def, MySQL extension
TABLE_SCHEMA
MySQL extension
PRIVILEGE_TYPE
MySQL extension
IS_GRANTABLE
MySQL extension
Notes:
• This is a nonstandard table. It takes its values from the mysql.db table.
15
16
Chapter 8 The INFORMATION_SCHEMA TABLE_PRIVILEGES
Table
The TABLE_PRIVILEGES table provides information about table privileges. This information comes from
the mysql.tables_priv grant table.
INFORMATION_SCHEMA Name
SHOW Name
Remarks
GRANTEE
'user_name'@'host_name'
value
TABLE_CATALOG
def
TABLE_SCHEMA
TABLE_NAME
PRIVILEGE_TYPE
IS_GRANTABLE
Notes:
• PRIVILEGE_TYPE can contain one (and only one) of these values: SELECT, INSERT, UPDATE,
REFERENCES, ALTER, INDEX, DROP, CREATE VIEW.
The following statements are not equivalent:
SELECT ... FROM INFORMATION_SCHEMA.TABLE_PRIVILEGES
SHOW GRANTS ...
17
18
Chapter 9 The INFORMATION_SCHEMA
COLUMN_PRIVILEGES Table
The COLUMN_PRIVILEGES table provides information about column privileges. This information comes
from the mysql.columns_priv grant table.
INFORMATION_SCHEMA Name
SHOW Name
Remarks
GRANTEE
'user_name'@'host_name'
value
TABLE_CATALOG
def
TABLE_SCHEMA
TABLE_NAME
COLUMN_NAME
PRIVILEGE_TYPE
IS_GRANTABLE
Notes:
• In the output from SHOW FULL COLUMNS, the privileges are all in one field and in lowercase, for
example, select,insert,update,references. In COLUMN_PRIVILEGES, there is one privilege per
row, in uppercase.
• PRIVILEGE_TYPE can contain one (and only one) of these values: SELECT, INSERT, UPDATE,
REFERENCES.
• If the user has GRANT OPTION privilege, IS_GRANTABLE should be YES. Otherwise, IS_GRANTABLE
should be NO. The output does not list GRANT OPTION as a separate privilege.
The following statements are not equivalent:
SELECT ... FROM INFORMATION_SCHEMA.COLUMN_PRIVILEGES
SHOW GRANTS ...
19
20
Chapter 10 The INFORMATION_SCHEMA CHARACTER_SETS
Table
The CHARACTER_SETS table provides information about available character sets.
INFORMATION_SCHEMA Name
SHOW Name
CHARACTER_SET_NAME
Charset
DEFAULT_COLLATE_NAME
Default collation
DESCRIPTION
Description
MySQL extension
MAXLEN
Maxlen
MySQL extension
The following statements are equivalent:
SELECT * FROM INFORMATION_SCHEMA.CHARACTER_SETS
[WHERE CHARACTER_SET_NAME LIKE 'wild']
SHOW CHARACTER SET
[LIKE 'wild']
21
Remarks
22
Chapter 11 The INFORMATION_SCHEMA COLLATIONS Table
The COLLATIONS table provides information about collations for each character set.
INFORMATION_SCHEMA Name
SHOW Name
Remarks
COLLATION_NAME
Collation
CHARACTER_SET_NAME
Charset
MySQL extension
ID
Id
MySQL extension
IS_DEFAULT
Default
MySQL extension
IS_COMPILED
Compiled
MySQL extension
SORTLEN
Sortlen
MySQL extension
• COLLATION_NAME is the collation name.
• CHARACTER_SET_NAME is the name of the character set with which the collation is associated.
• ID is the collation ID.
• IS_DEFAULT indicates whether the collation is the default for its character set.
• IS_COMPILED indicates whether the character set is compiled into the server.
• SORTLEN is related to the amount of memory required to sort strings expressed in the character set.
Collation information is also available from the SHOW COLLATION statement. The following statements are
equivalent:
SELECT COLLATION_NAME FROM INFORMATION_SCHEMA.COLLATIONS
[WHERE COLLATION_NAME LIKE 'wild']
SHOW COLLATION
[LIKE 'wild']
23
24
Chapter 12 The INFORMATION_SCHEMA
COLLATION_CHARACTER_SET_APPLICABILITY Table
The COLLATION_CHARACTER_SET_APPLICABILITY table indicates what character set is applicable
for what collation. The columns are equivalent to the first two display fields that we get from SHOW
COLLATION.
INFORMATION_SCHEMA Name
SHOW Name
COLLATION_NAME
Collation
CHARACTER_SET_NAME
Charset
25
Remarks
26
Chapter 13 The INFORMATION_SCHEMA
TABLE_CONSTRAINTS Table
The TABLE_CONSTRAINTS table describes which tables have constraints.
INFORMATION_SCHEMA Name
SHOW Name
CONSTRAINT_CATALOG
Remarks
def
CONSTRAINT_SCHEMA
CONSTRAINT_NAME
TABLE_SCHEMA
TABLE_NAME
CONSTRAINT_TYPE
Notes:
• The CONSTRAINT_TYPE value can be UNIQUE, PRIMARY KEY, or FOREIGN KEY.
• The UNIQUE and PRIMARY KEY information is about the same as what you get from the Key_name field
in the output from SHOW INDEX when the Non_unique field is 0.
• The CONSTRAINT_TYPE column can contain one of these values: UNIQUE, PRIMARY KEY, FOREIGN
KEY, CHECK. This is a CHAR (not ENUM) column. The CHECK value is not available until we support
CHECK.
27
28
Chapter 14 The INFORMATION_SCHEMA
KEY_COLUMN_USAGE Table
The KEY_COLUMN_USAGE table describes which key columns have constraints.
INFORMATION_SCHEMA Name
SHOW Name
CONSTRAINT_CATALOG
Remarks
def
CONSTRAINT_SCHEMA
CONSTRAINT_NAME
TABLE_CATALOG
def
TABLE_SCHEMA
TABLE_NAME
COLUMN_NAME
ORDINAL_POSITION
POSITION_IN_UNIQUE_CONSTRAINT
REFERENCED_TABLE_SCHEMA
REFERENCED_TABLE_NAME
REFERENCED_COLUMN_NAME
Notes:
• If the constraint is a foreign key, then this is the column of the foreign key, not the column that the foreign
key references.
• The value of ORDINAL_POSITION is the column's position within the constraint, not the column's
position within the table. Column positions are numbered beginning with 1.
• The value of POSITION_IN_UNIQUE_CONSTRAINT is NULL for unique and primary-key constraints. For
foreign-key constraints, it is the ordinal position in key of the table that is being referenced.
Suppose that there are two tables name t1 and t3 that have the following definitions:
CREATE TABLE t1
(
s1 INT,
s2 INT,
s3 INT,
PRIMARY KEY(s3)
) ENGINE=InnoDB;
CREATE TABLE t3
(
s1 INT,
s2 INT,
s3 INT,
KEY(s1),
CONSTRAINT CO FOREIGN KEY (s2) REFERENCES t1(s3)
) ENGINE=InnoDB;
For those two tables, the KEY_COLUMN_USAGE table has two rows:
• One row with CONSTRAINT_NAME = 'PRIMARY', TABLE_NAME = 't1', COLUMN_NAME = 's3',
ORDINAL_POSITION = 1, POSITION_IN_UNIQUE_CONSTRAINT = NULL.
29
• One row with CONSTRAINT_NAME = 'CO', TABLE_NAME = 't3', COLUMN_NAME = 's2',
ORDINAL_POSITION = 1, POSITION_IN_UNIQUE_CONSTRAINT = 1.
30
Chapter 15 The INFORMATION_SCHEMA ROUTINES Table
The ROUTINES table provides information about stored routines (both procedures and functions). The
ROUTINES table does not include user-defined functions (UDFs).
The column named “mysql.proc Name” indicates the mysql.proc table column that corresponds to the
INFORMATION_SCHEMA.ROUTINES table column, if any.
INFORMATION_SCHEMA Name
mysql.proc Name
SPECIFIC_NAME
specific_name
ROUTINE_CATALOG
Remarks
def
ROUTINE_SCHEMA
db
ROUTINE_NAME
name
ROUTINE_TYPE
type
{PROCEDURE|FUNCTION}
DATA_TYPE
same as for COLUMNS table
CHARACTER_MAXIMUM_LENGTH
same as for COLUMNS table
CHARACTER_OCTET_LENGTH
same as for COLUMNS table
NUMERIC_PRECISION
same as for COLUMNS table
NUMERIC_SCALE
same as for COLUMNS table
DATETIME_PRECISION
same as for COLUMNS table
CHARACTER_SET_NAME
same as for COLUMNS table
COLLATION_NAME
same as for COLUMNS table
DTD_IDENTIFIER
data type descriptor
ROUTINE_BODY
SQL
ROUTINE_DEFINITION
body_utf8
EXTERNAL_NAME
EXTERNAL_LANGUAGE
NULL
language
PARAMETER_STYLE
NULL
SQL
IS_DETERMINISTIC
is_deterministic
SQL_DATA_ACCESS
sql_data_access
SQL_PATH
NULL
SECURITY_TYPE
security_type
CREATED
created
LAST_ALTERED
modified
SQL_MODE
sql_mode
MySQL extension
ROUTINE_COMMENT
comment
MySQL extension
DEFINER
definer
MySQL extension
CHARACTER_SET_CLIENT
MySQL extension
COLLATION_CONNECTION
MySQL extension
DATABASE_COLLATION
MySQL extension
Notes:
31
• MySQL calculates EXTERNAL_LANGUAGE thus:
• If mysql.proc.language='SQL', EXTERNAL_LANGUAGE is NULL
• Otherwise, EXTERNAL_LANGUAGE is what is in mysql.proc.language. However, we do not have
external languages yet, so it is always NULL.
• CREATED: The date and time when the routine was created. This is a TIMESTAMP value.
• LAST_ALTERED: The date and time when the routine was last modified. This is a TIMESTAMP value. If
the routine has not been modified since its creation, this column holds the same value as the CREATED
column.
• SQL_MODE: The SQL mode in effect when the routine was created or altered, and under which the
routine executes. For the permitted values, see Server SQL Modes.
• CHARACTER_SET_CLIENT: The session value of the character_set_client system variable when
the routine was created.
• COLLATION_CONNECTION: The session value of the collation_connection system variable when
the routine was created.
• DATABASE_COLLATION: The collation of the database with which the routine is associated.
• The DATA_TYPE, CHARACTER_MAXIMUM_LENGTH, CHARACTER_OCTET_LENGTH,
NUMERIC_PRECISION, NUMERIC_SCALE, DATETIME_PRECISION, CHARACTER_SET_NAME, and
COLLATION_NAME columns provide information about the data type for the RETURNS clause of stored
functions. If a stored routine is a stored procedure, these columns all are NULL. DATETIME_PRECISION
was added in MySQL 5.6.4.
• Information about stored function RETURNS data types is also available in the PARAMETERS table. The
return value data type row for a function can be identified as the row that has an ORDINAL_POSITION
value of 0.
32
Chapter 16 The INFORMATION_SCHEMA VIEWS Table
The VIEWS table provides information about views in databases. You must have the SHOW VIEW privilege
to access this table.
INFORMATION_SCHEMA Name
SHOW Name
TABLE_CATALOG
Remarks
def
TABLE_SCHEMA
TABLE_NAME
VIEW_DEFINITION
CHECK_OPTION
IS_UPDATABLE
DEFINER
SECURITY_TYPE
CHARACTER_SET_CLIENT
MySQL extension
COLLATION_CONNECTION
MySQL extension
Notes:
• The VIEW_DEFINITION column has most of what you see in the Create Table field that SHOW
CREATE VIEW produces. Skip the words before SELECT and skip the words WITH CHECK OPTION.
Suppose that the original statement was:
CREATE VIEW v AS
SELECT s2,s1 FROM t
WHERE s1 > 5
ORDER BY s1
WITH CHECK OPTION;
Then the view definition looks like this:
SELECT s2,s1 FROM t WHERE s1 > 5 ORDER BY s1
• The CHECK_OPTION column has a value of NONE, CASCADE, or LOCAL.
• MySQL sets a flag, called the view updatability flag, at CREATE VIEW time. The flag is set to YES (true)
if UPDATE and DELETE (and similar operations) are legal for the view. Otherwise, the flag is set to NO
(false). The IS_UPDATABLE column in the VIEWS table displays the status of this flag. It means that the
server always knows whether a view is updatable.
If a view is not updatable, statements such UPDATE, DELETE, and INSERT are illegal and will be
rejected. (Note that even if a view is updatable, it might not be possible to insert into it; for details, refer
to Updatable and Insertable Views.)
• DEFINER: The account of the user who created the view, in 'user_name'@'host_name' format.
SECURITY_TYPE has a value of DEFINER or INVOKER.
• CHARACTER_SET_CLIENT: The session value of the character_set_client system variable when
the view was created.
• COLLATION_CONNECTION: The session value of the collation_connection system variable when
the view was created.
33
MySQL lets you use different sql_mode settings to tell the server the type of SQL syntax to support. For
example, you might use the ANSI SQL mode to ensure MySQL correctly interprets the standard SQL
concatenation operator, the double bar (||), in your queries. If you then create a view that concatenates
items, you might worry that changing the sql_mode setting to a value different from ANSI could cause
the view to become invalid. But this is not the case. No matter how you write out a view definition, MySQL
always stores it the same way, in a canonical form. Here is an example that shows how the server changes
a double bar concatenation operator to a CONCAT() function:
mysql> SET sql_mode = 'ANSI';
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE VIEW test.v AS SELECT 'a' || 'b' as col1;
Query OK, 0 rows affected (0.00 sec)
mysql> SELECT VIEW_DEFINITION FROM INFORMATION_SCHEMA.VIEWS
WHERE TABLE_SCHEMA = 'test' AND TABLE_NAME = 'v';
+----------------------------------+
| VIEW_DEFINITION
|
+----------------------------------+
| select concat('a','b') AS `col1` |
+----------------------------------+
1 row in set (0.00 sec)
The advantage of storing a view definition in canonical form is that changes made later to the value of
sql_mode will not affect the results from the view. However an additional consequence is that comments
prior to SELECT are stripped from the definition by the server.
34
Chapter 17 The INFORMATION_SCHEMA TRIGGERS Table
The TRIGGERS table provides information about triggers. To see information about a table's triggers, you
must have the TRIGGER privilege for the table.
INFORMATION_SCHEMA Name
SHOW Name
TRIGGER_CATALOG
Remarks
def
TRIGGER_SCHEMA
TRIGGER_NAME
Trigger
EVENT_MANIPULATION
Event
EVENT_OBJECT_CATALOG
def
EVENT_OBJECT_SCHEMA
EVENT_OBJECT_TABLE
Table
ACTION_ORDER
0
ACTION_CONDITION
NULL
ACTION_STATEMENT
Statement
ACTION_ORIENTATION
ACTION_TIMING
ROW
Timing
ACTION_REFERENCE_OLD_TABLE
NULL
ACTION_REFERENCE_NEW_TABLE
NULL
ACTION_REFERENCE_OLD_ROW
OLD
ACTION_REFERENCE_NEW_ROW
NEW
CREATED
Created
SQL_MODE
sql_mode
MySQL extension
DEFINER
Definer
MySQL extension
CHARACTER_SET_CLIENT
character_set_client
MySQL extension
COLLATION_CONNECTION
collation_connection
MySQL extension
DATABASE_COLLATION
Database Collation
MySQL extension
Notes:
• The names in the “SHOW Name” column refer to the SHOW TRIGGERS statement, not SHOW CREATE
TRIGGER. See SHOW TRIGGERS Syntax.
• TRIGGER_SCHEMA and TRIGGER_NAME: The name of the database in which the trigger occurs and the
trigger name, respectively.
• EVENT_MANIPULATION: The trigger event. This is the type of operation on the associated table for
which the trigger activates. The value is 'INSERT' (a row was inserted), 'DELETE' (a row was
deleted), or 'UPDATE' (a row was modified).
• EVENT_OBJECT_SCHEMA and EVENT_OBJECT_TABLE: As noted in Using Triggers, every trigger is
associated with exactly one table. These columns indicate the database in which this table occurs, and
the table name, respectively.
35
• ACTION_ORDER: The ordinal position of the trigger's action within the list of all similar triggers on the
same table. This value is always 0, because it is not possible to have more than one trigger with the
same EVENT_MANIPULATION and ACTION_TIMING on the same table.
• ACTION_STATEMENT: The trigger body; that is, the statement executed when the trigger activates. This
text uses UTF-8 encoding.
• ACTION_ORIENTATION: Always contains the value 'ROW'.
• ACTION_TIMING: Whether the trigger activates before or after the triggering event. The value is
'BEFORE' or 'AFTER'.
• ACTION_REFERENCE_OLD_ROW and ACTION_REFERENCE_NEW_ROW: The old and new column
identifiers, respectively. This means that ACTION_REFERENCE_OLD_ROW always contains the value
'OLD' and ACTION_REFERENCE_NEW_ROW always contains the value 'NEW'.
• SQL_MODE: The SQL mode in effect when the trigger was created, and under which the trigger executes.
For the permitted values, see Server SQL Modes.
• DEFINER: The account of the user who created the trigger, in 'user_name'@'host_name' format.
• CHARACTER_SET_CLIENT: The session value of the character_set_client system variable when
the trigger was created.
• COLLATION_CONNECTION: The session value of the collation_connection system variable when
the trigger was created.
• DATABASE_COLLATION: The collation of the database with which the trigger is associated.
• The following columns currently always contain NULL: ACTION_CONDITION,
ACTION_REFERENCE_OLD_TABLE, ACTION_REFERENCE_NEW_TABLE, and CREATED.
Example, using the ins_sum trigger defined in Using Triggers:
mysql> SELECT * FROM INFORMATION_SCHEMA.TRIGGERS
WHERE TRIGGER_SCHEMA='test' AND TRIGGER_NAME='ins_sum'\G
*************************** 1. row ***************************
TRIGGER_CATALOG: def
TRIGGER_SCHEMA: test
TRIGGER_NAME: ins_sum
EVENT_MANIPULATION: INSERT
EVENT_OBJECT_CATALOG: def
EVENT_OBJECT_SCHEMA: test
EVENT_OBJECT_TABLE: account
ACTION_ORDER: 0
ACTION_CONDITION: NULL
ACTION_STATEMENT: SET @sum = @sum + NEW.amount
ACTION_ORIENTATION: ROW
ACTION_TIMING: BEFORE
ACTION_REFERENCE_OLD_TABLE: NULL
ACTION_REFERENCE_NEW_TABLE: NULL
ACTION_REFERENCE_OLD_ROW: OLD
ACTION_REFERENCE_NEW_ROW: NEW
CREATED: NULL
SQL_MODE: NO_ENGINE_SUBSTITUTION
DEFINER: me@localhost
CHARACTER_SET_CLIENT: utf8
COLLATION_CONNECTION: utf8_general_ci
DATABASE_COLLATION: latin1_swedish_ci
36
Chapter 18 The INFORMATION_SCHEMA PLUGINS Table
The PLUGINS table provides information about server plugins.
INFORMATION_SCHEMA Name
SHOW Name
Remarks
PLUGIN_NAME
Name
MySQL extension
MySQL extension
PLUGIN_VERSION
PLUGIN_STATUS
Status
MySQL extension
PLUGIN_TYPE
Type
MySQL extension
MySQL extension
PLUGIN_TYPE_VERSION
PLUGIN_LIBRARY
Library
MySQL extension
PLUGIN_LIBRARY_VERSION
MySQL extension
PLUGIN_AUTHOR
MySQL extension
PLUGIN_DESCRIPTION
MySQL extension
PLUGIN_LICENSE
License
MySQL extension
MySQL extension
LOAD_OPTION
Notes:
• The PLUGINS table is a nonstandard table.
• PLUGIN_NAME is the name used to refer to the plugin in statements such as INSTALL PLUGIN and
UNINSTALL PLUGIN.
• PLUGIN_VERSION is the version from the plugin's general type descriptor.
• PLUGIN_STATUS indicates the plugin status, one of ACTIVE, INACTIVE, DISABLED, or DELETED.
• PLUGIN_TYPE indicates the type of plugin, such as STORAGE ENGINE, INFORMATION_SCHEMA, or
AUTHENTICATION.
• PLUGIN_TYPE_VERSION is the version from the plugin's type-specific descriptor.
• PLUGIN_LIBRARY is the name of the plugin shared library file. This is the name used to refer to the
plugin file in statements such as INSTALL PLUGIN and UNINSTALL PLUGIN. This file is located in the
directory named by the plugin_dir system variable. If the library name is NULL, the plugin is compiled
in and cannot be uninstalled with UNINSTALL PLUGIN.
• PLUGIN_LIBRARY_VERSION indicates the plugin API interface version.
• PLUGIN_AUTHOR names the plugin author.
• PLUGIN_DESCRIPTION provides a short description of the plugin.
• PLUGIN_LICENSE indicates how the plugin is licensed; for example, GPL.
• LOAD_OPTION indicates how the plugin was loaded. The value is OFF, ON, FORCE, or
FORCE_PLUS_PERMANENT. See Installing and Uninstalling Plugins.
For plugins installed with INSTALL PLUGIN, the PLUGIN_NAME and PLUGIN_LIBRARY values are also
registered in the mysql.plugin table.
37
These statements are equivalent:
SELECT
PLUGIN_NAME, PLUGIN_STATUS, PLUGIN_TYPE,
PLUGIN_LIBRARY, PLUGIN_LICENSE
FROM INFORMATION_SCHEMA.PLUGINS;
SHOW PLUGINS;
For information about plugin data structures that form the basis of the information in the PLUGINS table,
see The MySQL Plugin API.
Plugin information is also available using the SHOW PLUGINS statement. See SHOW PLUGINS Syntax.
38
Chapter 19 The INFORMATION_SCHEMA ENGINES Table
The ENGINES table provides information about storage engines.
INFORMATION_SCHEMA Name
SHOW Name
Remarks
ENGINE
Engine
MySQL extension
SUPPORT
Support
MySQL extension
COMMENT
Comment
MySQL extension
TRANSACTIONS
Transactions
MySQL extension
XA
XA
MySQL extension
SAVEPOINTS
Savepoints
MySQL extension
Notes:
• The ENGINES table is a nonstandard table. Its contents correspond to the columns of the SHOW
ENGINES statement. For descriptions of its columns, see SHOW ENGINES Syntax.
See also SHOW ENGINES Syntax.
39
40
Chapter 20 The INFORMATION_SCHEMA PARTITIONS Table
The PARTITIONS table provides information about table partitions. See Partitioning, for more information
about partitioning tables.
INFORMATION_SCHEMA Name
SHOW Name
Remarks
TABLE_CATALOG
MySQL extension
TABLE_SCHEMA
MySQL extension
TABLE_NAME
MySQL extension
PARTITION_NAME
MySQL extension
SUBPARTITION_NAME
MySQL extension
PARTITION_ORDINAL_POSITION
MySQL extension
SUBPARTITION_ORDINAL_POSITION
MySQL extension
PARTITION_METHOD
MySQL extension
SUBPARTITION_METHOD
MySQL extension
PARTITION_EXPRESSION
MySQL extension
SUBPARTITION_EXPRESSION
MySQL extension
PARTITION_DESCRIPTION
MySQL extension
TABLE_ROWS
MySQL extension
AVG_ROW_LENGTH
MySQL extension
DATA_LENGTH
MySQL extension
MAX_DATA_LENGTH
MySQL extension
INDEX_LENGTH
MySQL extension
DATA_FREE
MySQL extension
CREATE_TIME
MySQL extension
UPDATE_TIME
MySQL extension
CHECK_TIME
MySQL extension
CHECKSUM
MySQL extension
PARTITION_COMMENT
MySQL extension
NODEGROUP
MySQL extension
TABLESPACE_NAME
MySQL extension
Notes:
• The PARTITIONS table is a nonstandard table.
Each record in this table corresponds to an individual partition or subpartition of a partitioned table.
• TABLE_CATALOG: This column is always def.
• TABLE_SCHEMA: This column contains the name of the database to which the table belongs.
• TABLE_NAME: This column contains the name of the table containing the partition.
• PARTITION_NAME: The name of the partition.
41
• SUBPARTITION_NAME: If the PARTITIONS table record represents a subpartition, then this column
contains the name of subpartition; otherwise it is NULL.
• PARTITION_ORDINAL_POSITION: All partitions are indexed in the same order as they are defined,
with 1 being the number assigned to the first partition. The indexing can change as partitions are added,
dropped, and reorganized; the number shown is this column reflects the current order, taking into
account any indexing changes.
• SUBPARTITION_ORDINAL_POSITION: Subpartitions within a given partition are also indexed and
reindexed in the same manner as partitions are indexed within a table.
• PARTITION_METHOD: One of the values RANGE, LIST, HASH, LINEAR HASH, KEY, or LINEAR KEY;
that is, one of the available partitioning types as discussed in Partitioning Types.
• SUBPARTITION_METHOD: One of the values HASH, LINEAR HASH, KEY, or LINEAR KEY; that is, one of
the available subpartitioning types as discussed in Subpartitioning.
• PARTITION_EXPRESSION: This is the expression for the partitioning function used in the CREATE
TABLE or ALTER TABLE statement that created the table's current partitioning scheme.
For example, consider a partitioned table created in the test database using this statement:
CREATE TABLE tp (
c1 INT,
c2 INT,
c3 VARCHAR(25)
)
PARTITION BY HASH(c1 + c2)
PARTITIONS 4;
The PARTITION_EXPRESSION column in a PARTITIONS table record for a partition from this table
displays c1 + c2, as shown here:
mysql> SELECT DISTINCT PARTITION_EXPRESSION
>
FROM INFORMATION_SCHEMA.PARTITIONS
>
WHERE TABLE_NAME='tp' AND TABLE_SCHEMA='test';
+----------------------+
| PARTITION_EXPRESSION |
+----------------------+
| c1 + c2
|
+----------------------+
1 row in set (0.09 sec)
• SUBPARTITION_EXPRESSION: This works in the same fashion for the subpartitioning expression that
defines the subpartitioning for a table as PARTITION_EXPRESSION does for the partitioning expression
used to define a table's partitioning.
If the table has no subpartitions, then this column is NULL.
• PARTITION_DESCRIPTION: This column is used for RANGE and LIST partitions. For a RANGE partition,
it contains the value set in the partition's VALUES LESS THAN clause, which can be either an integer or
MAXVALUE. For a LIST partition, this column contains the values defined in the partition's VALUES IN
clause, which is a comma-separated list of integer values.
For partitions whose PARTITION_METHOD is other than RANGE or LIST, this column is always NULL.
• TABLE_ROWS: The number of table rows in the partition.
42
For partitioned InnoDB tables, the row count given in the TABLE_ROWS column is only an estimated
value used in SQL optimization, and may not always be exact.
• AVG_ROW_LENGTH: The average length of the rows stored in this partition or subpartition, in bytes.
This is the same as DATA_LENGTH divided by TABLE_ROWS.
• DATA_LENGTH: The total length of all rows stored in this partition or subpartition, in bytes—that is, the
total number of bytes stored in the partition or subpartition.
• MAX_DATA_LENGTH: The maximum number of bytes that can be stored in this partition or subpartition.
• INDEX_LENGTH: The length of the index file for this partition or subpartition, in bytes.
• DATA_FREE: The number of bytes allocated to the partition or subpartition but not used.
• CREATE_TIME: The time of the partition's or subpartition's creation.
Prior to MySQL 5.6.25, for partitioned InnoDB tables, this column was always NULL. The correct
creation time is shown in MySQL 5.6.25 and later. (Bug #17299181, Bug #69990)
• UPDATE_TIME: The time that the partition or subpartition was last modified.
For partitioned InnoDB tables, this column is always NULL.
• CHECK_TIME: The last time that the table to which this partition or subpartition belongs was checked.
For partitioned InnoDB tables, this column is always NULL.
• CHECKSUM: The checksum value, if any; otherwise, this column is NULL.
• PARTITION_COMMENT: This column contains the text of any comment made for the partition.
Prior to MySQL 5.6.6, the display width of this column was 80 characters, and partition comments
which exceeded this length were truncated to fit. As of MySQL 5.6.6, the maximum length for a partition
comment is defined as 1024 characters, and the display width of the PARTITION_COMMENT column is
increased to 1024 characters to match this limit (Bug #11748924, Bug #37728).
The default value for this column is an empty string.
• NODEGROUP: This is the nodegroup to which the partition belongs. This is relevant only to NDB Cluster
tables; otherwise the value of this column is always 0.
• TABLESPACE_NAME: This column contains the name of the tablespace to which the partition belongs.
The value of this column is always DEFAULT.
• A nonpartitioned table has one record in INFORMATION_SCHEMA.PARTITIONS; however, the
values of the PARTITION_NAME, SUBPARTITION_NAME, PARTITION_ORDINAL_POSITION,
SUBPARTITION_ORDINAL_POSITION, PARTITION_METHOD, SUBPARTITION_METHOD,
PARTITION_EXPRESSION, SUBPARTITION_EXPRESSION, and PARTITION_DESCRIPTION columns
are all NULL. (The PARTITION_COMMENT column in this case is blank.)
43
44
Chapter 21 The INFORMATION_SCHEMA EVENTS Table
The EVENTS table provides information about scheduled events, which are discussed in Using the Event
Scheduler. The SHOW Name values correspond to column names of the SHOW EVENTS statement.
INFORMATION_SCHEMA Name
SHOW Name
Remarks
def, MySQL extension
EVENT_CATALOG
EVENT_SCHEMA
Db
MySQL extension
EVENT_NAME
Name
MySQL extension
DEFINER
Definer
MySQL extension
TIME_ZONE
Time zone
MySQL extension
EVENT_BODY
MySQL extension
EVENT_DEFINITION
MySQL extension
EVENT_TYPE
Type
MySQL extension
EXECUTE_AT
Execute at
MySQL extension
INTERVAL_VALUE
Interval value
MySQL extension
INTERVAL_FIELD
Interval field
MySQL extension
MySQL extension
SQL_MODE
STARTS
Starts
MySQL extension
ENDS
Ends
MySQL extension
STATUS
Status
MySQL extension
ON_COMPLETION
MySQL extension
CREATED
MySQL extension
LAST_ALTERED
MySQL extension
LAST_EXECUTED
MySQL extension
EVENT_COMMENT
MySQL extension
ORIGINATOR
Originator
MySQL extension
CHARACTER_SET_CLIENT
character_set_client
MySQL extension
COLLATION_CONNECTION
collation_connection
MySQL extension
DATABASE_COLLATION
Database Collation
MySQL extension
Notes:
• The EVENTS table is a nonstandard table.
• EVENT_CATALOG: The value of this column is always def.
• EVENT_SCHEMA: The name of the schema (database) to which this event belongs.
• EVENT_NAME: The name of the event.
• DEFINER: The account of the user who created the event, in 'user_name'@'host_name' format.
• TIME_ZONE: The event time zone, which is the time zone used for scheduling the event and that is in
effect within the event as it executes. The default value is SYSTEM.
45
• EVENT_BODY: The language used for the statements in the event's DO clause; in MySQL 5.6, this is
always SQL.
This column is not to be confused with the column of the same name (now named EVENT_DEFINITION)
that existed in earlier MySQL versions.
• EVENT_DEFINITION: The text of the SQL statement making up the event's DO clause; in other words,
the statement executed by this event.
• EVENT_TYPE: The event repetition type, either ONE TIME (transient) or RECURRING (repeating).
• EXECUTE_AT: For a one-time event, this is the DATETIME value specified in the AT clause of the
CREATE EVENT statement used to create the event, or of the last ALTER EVENT statement that
modified the event. The value shown in this column reflects the addition or subtraction of any INTERVAL
value included in the event's AT clause. For example, if an event is created using ON SCHEDULE AT
CURRENT_TIMESTAMP + '1:6' DAY_HOUR, and the event was created at 2006-02-09 14:05:30, the
value shown in this column would be '2006-02-10 20:05:30'.
If the event's timing is determined by an EVERY clause instead of an AT clause (that is, if the event is
recurring), the value of this column is NULL.
• INTERVAL_VALUE: For recurring events, this column contains the numeric portion of the event's EVERY
clause.
For a one-time event (that is, an event whose timing is determined by an AT clause), this column is
NULL.
• INTERVAL_FIELD: For recurring events, this column contains the units portion of the EVERY clause
governing the timing of the event. Thus, this column contains a value such as 'YEAR', 'QUARTER', 'DAY',
and so on.
For a one-time event (that is, an event whose timing is determined by an AT clause), this column is
NULL.
• SQL_MODE: The SQL mode in effect when the event was created or altered, and under which the event
executes. For the permitted values, see Server SQL Modes.
• STARTS: For a recurring event whose definition includes a STARTS clause, this column contains the
corresponding DATETIME value. As with the EXECUTE_AT column, this value resolves any expressions
used.
If there is no STARTS clause affecting the timing of the event, this column is NULL
• ENDS: For a recurring event whose definition includes a ENDS clause, this column contains the
corresponding DATETIME value. As with the EXECUTE_AT column, this value resolves any expressions
used.
If there is no ENDS clause affecting the timing of the event, this column is NULL.
• STATUS: One of the three values ENABLED, DISABLED, or SLAVESIDE_DISABLED.
SLAVESIDE_DISABLED indicates that the creation of the event occurred on another MySQL server
acting as a replication master and was replicated to the current MySQL server which is acting as a slave,
but the event is not presently being executed on the slave. See Replication of Invoked Features, for
more information.
• ON_COMPLETION: One of the two values PRESERVE or NOT PRESERVE.
46
• CREATED: The date and time when the event was created. This is a TIMESTAMP value.
• LAST_ALTERED: The date and time when the event was last modified. This is a TIMESTAMP value. If
the event has not been modified since its creation, this column holds the same value as the CREATED
column.
• LAST_EXECUTED: The date and time when the event last executed. A DATETIME value. If the event has
never executed, this column is NULL.
LAST_EXECUTED indicates when the event started. As a result, the ENDS column is never less than
LAST_EXECUTED.
• EVENT_COMMENT: The text of a comment, if the event has one. If not, the value of this column is an
empty string.
• ORIGINATOR: The server ID of the MySQL server on which the event was created; used in replication.
The default value is 0.
• CHARACTER_SET_CLIENT: The session value of the character_set_client system variable when
the event was created.
• COLLATION_CONNECTION: The session value of the collation_connection system variable when
the event was created.
• DATABASE_COLLATION: The collation of the database with which the event is associated.
Example: Suppose that the user jon@ghidora creates an event named e_daily, and then modifies it a
few minutes later using an ALTER EVENT statement, as shown here:
DELIMITER |
CREATE EVENT e_daily
ON SCHEDULE
EVERY 1 DAY
COMMENT 'Saves total number of sessions then clears the table each day'
DO
BEGIN
INSERT INTO site_activity.totals (time, total)
SELECT CURRENT_TIMESTAMP, COUNT(*)
FROM site_activity.sessions;
DELETE FROM site_activity.sessions;
END |
DELIMITER ;
ALTER EVENT e_daily
ENABLE;
(Note that comments can span multiple lines.)
This user can then run the following SELECT statement, and obtain the output shown:
mysql> SELECT * FROM INFORMATION_SCHEMA.EVENTS
> WHERE EVENT_NAME = 'e_daily'
> AND EVENT_SCHEMA = 'myschema'\G
*************************** 1. row ***************************
EVENT_CATALOG: def
EVENT_SCHEMA: test
EVENT_NAME: e_daily
DEFINER: me@localhost
TIME_ZONE: SYSTEM
EVENT_BODY: SQL
EVENT_DEFINITION: BEGIN
47
INSERT INTO site_activity.totals (time, total)
SELECT CURRENT_TIMESTAMP, COUNT(*)
FROM site_activity.sessions;
DELETE FROM site_activity.sessions;
END
EVENT_TYPE: RECURRING
EXECUTE_AT: NULL
INTERVAL_VALUE: 1
INTERVAL_FIELD: DAY
SQL_MODE:
STARTS: 2008-09-03 12:13:39
ENDS: NULL
STATUS: ENABLED
ON_COMPLETION: NOT PRESERVE
CREATED: 2008-09-03 12:13:39
LAST_ALTERED: 2008-09-03 12:13:39
LAST_EXECUTED: NULL
EVENT_COMMENT: Saves total number of sessions then clears the
table each day
ORIGINATOR: 1
CHARACTER_SET_CLIENT: latin1
COLLATION_CONNECTION: latin1_swedish_ci
DATABASE_COLLATION: latin1_swedish_ci
Times in the EVENTS table are displayed using the event time zone or the current session time zone, as
described in Event Metadata.
See also SHOW EVENTS Syntax.
48
Chapter 22 The INFORMATION_SCHEMA FILES Table
The FILES table provides information about the files in which MySQL NDB Disk Data tables are stored.
Note
This table provides information about Disk Data files only; you cannot use it for
determining disk space allocation or availability for individual NDB tables. However,
it is possible to see how much space is allocated for each NDB table having data
stored on disk—as well as how much remains available for storage of data on disk
for that table—using ndb_desc. For more information, see ndb_desc — Describe
NDB Tables.
INFORMATION_SCHEMA Name
SHOW Name
Remarks
FILE_ID
MySQL extension
FILE_NAME
MySQL extension
FILE_TYPE
MySQL extension
TABLESPACE_NAME
MySQL extension
TABLE_CATALOG
MySQL extension
TABLE_SCHEMA
MySQL extension
TABLE_NAME
MySQL extension
LOGFILE_GROUP_NAME
MySQL extension
LOGFILE_GROUP_NUMBER
MySQL extension
ENGINE
MySQL extension
FULLTEXT_KEYS
MySQL extension
DELETED_ROWS
MySQL extension
UPDATE_COUNT
MySQL extension
FREE_EXTENTS
MySQL extension
TOTAL_EXTENTS
MySQL extension
EXTENT_SIZE
MySQL extension
INITIAL_SIZE
MySQL extension
MAXIMUM_SIZE
MySQL extension
AUTOEXTEND_SIZE
MySQL extension
CREATION_TIME
MySQL extension
LAST_UPDATE_TIME
MySQL extension
LAST_ACCESS_TIME
MySQL extension
RECOVER_TIME
MySQL extension
TRANSACTION_COUNTER
MySQL extension
VERSION
MySQL extension
ROW_FORMAT
MySQL extension
TABLE_ROWS
MySQL extension
AVG_ROW_LENGTH
MySQL extension
DATA_LENGTH
MySQL extension
49
INFORMATION_SCHEMA Name
SHOW Name
Remarks
MAX_DATA_LENGTH
MySQL extension
INDEX_LENGTH
MySQL extension
DATA_FREE
MySQL extension
CREATE_TIME
MySQL extension
UPDATE_TIME
MySQL extension
CHECK_TIME
MySQL extension
CHECKSUM
MySQL extension
STATUS
MySQL extension
EXTRA
MySQL extension
Notes:
• FILE_ID column values are auto-generated.
• FILE_NAME is the name of an UNDO log file created by CREATE LOGFILE GROUP or ALTER LOGFILE
GROUP, or of a data file created by CREATE TABLESPACE or ALTER TABLESPACE.
• FILE_TYPE is one of the values UNDOFILE, DATAFILE, or TABLESPACE.
• TABLESPACE_NAME is the name of the tablespace with which the file is associated.
• The value of the TABLESPACE_CATALOG column is always NULL.
• TABLE_NAME is the name of the Disk Data table with which the file is associated, if any.
• The LOGFILE_GROUP_NAME column gives the name of the log file group to which the log file or data file
belongs.
• For an UNDO log file, the LOGFILE_GROUP_NUMBER contains the auto-generated ID number of the log
file group to which the log file belongs.
• For an NDB Cluster Disk Data log file or data file, the value of the ENGINE column is always NDB or
NDBCLUSTER.
• For an NDB Cluster Disk Data log file or data file, the value of the FULLTEXT_KEYS column is always
empty.
• The FREE EXTENTS column displays the number of extents which have not yet been used by the file.
The TOTAL EXTENTS column show the total number of extents allocated to the file.
The difference between these two columns is the number of extents currently in use by the file:
SELECT TOTAL_EXTENTS - FREE_EXTENTS AS extents_used
FROM INFORMATION_SCHEMA.FILES
WHERE FILE_NAME = 'myfile.dat';
You can approximate the amount of disk space in use by the file by multiplying this difference by the
value of the EXTENT_SIZE column, which gives the size of an extent for the file in bytes:
SELECT (TOTAL_EXTENTS - FREE_EXTENTS) * EXTENT_SIZE AS bytes_used
FROM INFORMATION_SCHEMA.FILES
WHERE FILE_NAME = 'myfile.dat';
50
Similarly, you can estimate the amount of space that remains available in a given file by multiplying
FREE_EXTENTS by EXTENT_SIZE:
SELECT FREE_EXTENTS * EXTENT_SIZE AS bytes_free
FROM INFORMATION_SCHEMA.FILES
WHERE FILE_NAME = 'myfile.dat';
Important
The byte values produced by the preceding queries are approximations only, and
their precision is inversely proportional to the value of EXTENT_SIZE. That is, the
larger EXTENT_SIZE becomes, the less accurate the approximations are.
It is also important to remember that once an extent is used, it cannot be freed again without dropping
the data file of which it is a part. This means that deletes from a Disk Data table do not release disk
space.
The extent size can be set in a CREATE TABLESPACE statement. See CREATE TABLESPACE Syntax,
for more information.
• The INITIAL_SIZE column shows the size in bytes of the file. This is the same value that was used
in the INITIAL_SIZE clause of the CREATE LOGFILE GROUP, ALTER LOGFILE GROUP, CREATE
TABLESPACE, or ALTER TABLESPACE statement used to create the file.
For NDB Cluster Disk Data files, the value of the MAXIMUM_SIZE column is always the same as
INITIAL_SIZE, and the AUTOEXTEND_SIZE column is always empty.
• The CREATION_TIME column shows the date and time when the file was created. The
LAST_UPDATE_TIME column displays the date and time when the file was last modified. The
LAST_ACCESSED column provides the date and time when the file was last accessed by the server.
The values of these columns are as reported by the operating system, and are not supplied by the
NDB storage engine. Where no value is provided by the operating system, these columns display
0000-00-00 00:00:00.
• For NDB Cluster Disk Data files, the value of the RECOVER_TIME and TRANSACTION_COUNTER
columns is always 0.
• For NDB Cluster Disk Data files, the following columns are always NULL:
• VERSION
• ROW_FORMAT
• TABLE_ROWS
• AVG_ROW_LENGTH
• DATA_LENGTH
• MAX_DATA_LENGTH
• INDEX_LENGTH
• DATA_FREE
51
• CREATE_TIME
• UPDATE_TIME
• CHECK_TIME
• CHECKSUM
• For NDB Cluster Disk Data files, the value of the STATUS column is always NORMAL.
• For NDB Cluster Disk Data files, the EXTRA column shows which data node the file belongs to, as each
data node has its own copy of the file. Suppose that you use this statement on an NDB Cluster with four
data nodes:
CREATE LOGFILE GROUP mygroup
ADD UNDOFILE 'new_undo.dat'
INITIAL_SIZE 2G
ENGINE NDB;
After running the CREATE LOGFILE GROUP statement successfully, you should see a result similar to
the one shown here for this query against the FILES table:
mysql> SELECT LOGFILE_GROUP_NAME, FILE_TYPE, EXTRA
->
FROM INFORMATION_SCHEMA.FILES
->
WHERE FILE_NAME = 'new_undo.dat';
+--------------------+-------------+----------------+
| LOGFILE_GROUP_NAME | FILE_TYPE
| EXTRA
|
+--------------------+-------------+----------------+
| mygroup
| UNDO FILE
| CLUSTER_NODE=3 |
| mygroup
| UNDO FILE
| CLUSTER_NODE=4 |
| mygroup
| UNDO FILE
| CLUSTER_NODE=5 |
| mygroup
| UNDO FILE
| CLUSTER_NODE=6 |
+--------------------+-------------+----------------+
4 rows in set (0.01 sec)
• The FILES table is a nonstandard table.
• An additional row is present in the FILES table following the creation of a logfile group. This row has
NULL for the value of the FILE_NAME column. For this row, the value of the FILE_ID column is always
0, that of the FILE_TYPE column is always UNDO FILE, and that of the STATUS column is always
NORMAL. The value of the ENGINE column is always NDBCLUSTER.
The FREE_EXTENTS column in this row shows the total number of free extents available to all undo files
belonging to a given log file group whose name and number are shown in the LOGFILE_GROUP_NAME
and LOGFILE_GROUP_NUMBER columns, respectively.
Suppose there are no existing log file groups on your NDB Cluster, and you create one using the
following statement:
mysql> CREATE LOGFILE GROUP lg1
->
ADD UNDOFILE 'undofile.dat'
->
INITIAL_SIZE = 16M
->
UNDO_BUFFER_SIZE = 1M
->
ENGINE = NDB;
Query OK, 0 rows affected (3.81 sec)
You can now see this NULL row when you query the FILES table:
52
mysql> SELECT DISTINCT
->
FILE_NAME AS File,
->
FREE_EXTENTS AS Free,
->
TOTAL_EXTENTS AS Total,
->
EXTENT_SIZE AS Size,
->
INITIAL_SIZE AS Initial
->
FROM INFORMATION_SCHEMA.FILES;
+--------------+---------+---------+------+----------+
| File
| Free
| Total
| Size | Initial |
+--------------+---------+---------+------+----------+
| undofile.dat |
NULL | 4194304 |
4 | 16777216 |
| NULL
| 4184068 |
NULL |
4 |
NULL |
+--------------+---------+---------+------+----------+
2 rows in set (0.01 sec)
The total number of free extents available for undo logging is always somewhat less than the sum of
the TOTAL_EXTENTS column values for all undo files in the log file group due to overhead required for
maintaining the undo files. This can be seen by adding a second undo file to the log file group, then
repeating the previous query against the FILES table:
mysql> ALTER LOGFILE GROUP lg1
->
ADD UNDOFILE 'undofile02.dat'
->
INITIAL_SIZE = 4M
->
ENGINE = NDB;
Query OK, 0 rows affected (1.02 sec)
mysql> SELECT DISTINCT
->
FILE_NAME AS File,
->
FREE_EXTENTS AS Free,
->
TOTAL_EXTENTS AS Total,
->
EXTENT_SIZE AS Size,
->
INITIAL_SIZE AS Initial
->
FROM INFORMATION_SCHEMA.FILES;
+----------------+---------+---------+------+----------+
| File
| Free
| Total
| Size | Initial |
+----------------+---------+---------+------+----------+
| undofile.dat
|
NULL | 4194304 |
4 | 16777216 |
| undofile02.dat |
NULL | 1048576 |
4 | 4194304 |
| NULL
| 5223944 |
NULL |
4 |
NULL |
+----------------+---------+---------+------+----------+
3 rows in set (0.01 sec)
The amount of free space in bytes which is available for undo logging by Disk Data tables using this log
file group can be approximated by multiplying the number of free extents by the initial size:
mysql> SELECT
->
FREE_EXTENTS AS 'Free Extents',
->
FREE_EXTENTS * EXTENT_SIZE AS 'Free Bytes'
->
FROM INFORMATION_SCHEMA.FILES
->
WHERE LOGFILE_GROUP_NAME = 'lg1'
->
AND FILE_NAME IS NULL;
+--------------+------------+
| Free Extents | Free Bytes |
+--------------+------------+
|
5223944 |
20895776 |
+--------------+------------+
1 row in set (0.02 sec)
If you create an NDB Cluster Disk Data table and then insert some rows into it, you can see
approximately how much space remains for undo logging afterward, for example:
53
mysql> CREATE TABLESPACE ts1
->
ADD DATAFILE 'data1.dat'
->
USE LOGFILE GROUP lg1
->
INITIAL_SIZE 512M
->
ENGINE = NDB;
Query OK, 0 rows affected (8.71 sec)
mysql> CREATE TABLE dd (
->
c1 INT NOT NULL PRIMARY KEY,
->
c2 INT,
->
c3 DATE
->
)
->
TABLESPACE ts1 STORAGE DISK
->
ENGINE = NDB;
Query OK, 0 rows affected (2.11 sec)
mysql> INSERT INTO dd VALUES
->
(NULL, 1234567890, '2007-02-02'),
->
(NULL, 1126789005, '2007-02-03'),
->
(NULL, 1357924680, '2007-02-04'),
->
(NULL, 1642097531, '2007-02-05');
Query OK, 4 rows affected (0.01 sec)
mysql> SELECT
->
FREE_EXTENTS AS 'Free Extents',
->
FREE_EXTENTS * EXTENT_SIZE AS 'Free Bytes'
->
FROM INFORMATION_SCHEMA.FILES
->
WHERE LOGFILE_GROUP_NAME = 'lg1'
->
AND FILE_NAME IS NULL;
+--------------+------------+
| Free Extents | Free Bytes |
+--------------+------------+
|
5207565 |
20830260 |
+--------------+------------+
1 row in set (0.01 sec)
• An additional row is present in the FILES table for any NDB Cluster tablespace, whether or not any data
files are associated with the tablespace. This row has NULL for the value of the FILE_NAME column.
For this row, the value of the FILE_ID column is always 0, that of the FILE_TYPE column is always
TABLESPACE, and that of the STATUS column is always NORMAL. The value of the ENGINE column is
always NDBCLUSTER.
• There are no SHOW statements associated with the FILES table.
• For additional information, and examples of creating and dropping NDB Cluster Disk Data objects, see
NDB Cluster Disk Data Tables.
54
Chapter 23 The INFORMATION_SCHEMA PROCESSLIST
Table
The PROCESSLIST table provides information about which threads are running.
INFORMATION_SCHEMA Name
SHOW Name
Remarks
ID
Id
MySQL extension
USER
User
MySQL extension
HOST
Host
MySQL extension
DB
db
MySQL extension
COMMAND
Command
MySQL extension
TIME
Time
MySQL extension
STATE
State
MySQL extension
INFO
Info
MySQL extension
For an extensive description of the table columns, see SHOW PROCESSLIST Syntax.
Notes:
• The PROCESSLIST table is a nonstandard table.
• Like the output from the corresponding SHOW statement, the PROCESSLIST table will only show
information about your own threads, unless you have the PROCESS privilege, in which case you will see
information about other threads, too. As an anonymous user, you cannot see any rows at all.
• If an SQL statement refers to INFORMATION_SCHEMA.PROCESSLIST, MySQL populates the entire
table once, when statement execution begins, so there is read consistency during the statement. There
is no read consistency for a multi-statement transaction, though.
• Process information is also available from the performance_schema.threads table. However,
access to threads does not require a mutex and has minimal impact on server performance.
INFORMATION_SCHEMA.PROCESSLIST and SHOW PROCESSLIST have negative performance
consequences because they require a mutex. threads also shows information about background
threads, which INFORMATION_SCHEMA.PROCESSLIST and SHOW PROCESSLIST do not. This means
that threads can be used to monitor activity the other thread information sources cannot.
The following statements are equivalent:
SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST
SHOW FULL PROCESSLIST
55
56
Chapter 24 The INFORMATION_SCHEMA
REFERENTIAL_CONSTRAINTS Table
The REFERENTIAL_CONSTRAINTS table provides information about foreign keys.
INFORMATION_SCHEMA Name
SHOW Name
CONSTRAINT_CATALOG
Remarks
def
CONSTRAINT_SCHEMA
CONSTRAINT_NAME
UNIQUE_CONSTRAINT_CATALOG
def
UNIQUE_CONSTRAINT_SCHEMA
UNIQUE_CONSTRAINT_NAME
MATCH_OPTION
UPDATE_RULE
DELETE_RULE
TABLE_NAME
REFERENCED_TABLE_NAME
Notes:
• TABLE_NAME has the same value as TABLE_NAME in INFORMATION_SCHEMA.TABLE_CONSTRAINTS.
• CONSTRAINT_SCHEMA and CONSTRAINT_NAME identify the foreign key.
• UNIQUE_CONSTRAINT_SCHEMA, UNIQUE_CONSTRAINT_NAME, and REFERENCED_TABLE_NAME
identify the referenced key.
• The only valid value at this time for MATCH_OPTION is NONE.
• The possible values for UPDATE_RULE or DELETE_RULE are CASCADE, SET NULL, SET DEFAULT,
RESTRICT, NO ACTION.
57
58
Chapter 25 The INFORMATION_SCHEMA GLOBAL_STATUS
and SESSION_STATUS Tables
The GLOBAL_STATUS and SESSION_STATUS tables provide information about server status variables.
Their contents correspond to the information produced by the SHOW GLOBAL STATUS and SHOW
SESSION STATUS statements (see SHOW STATUS Syntax).
INFORMATION_SCHEMA Name
SHOW Name
VARIABLE_NAME
Variable_name
VARIABLE_VALUE
Value
Remarks
Notes:
• The VARIABLE_VALUE column for each of these tables is defined as VARCHAR(1024).
59
60
Chapter 26 The INFORMATION_SCHEMA
GLOBAL_VARIABLES and SESSION_VARIABLES Tables
The GLOBAL_VARIABLES and SESSION_VARIABLES tables provide information about server status
variables. Their contents correspond to the information produced by the SHOW GLOBAL VARIABLES and
SHOW SESSION VARIABLES statements (see SHOW VARIABLES Syntax).
INFORMATION_SCHEMA Name
SHOW Name
VARIABLE_NAME
Variable_name
VARIABLE_VALUE
Value
Remarks
Notes:
• The VARIABLE_VALUE column for each of these tables is defined as VARCHAR(1024). For variables
with very long values that are not completely displayed, use SELECT as a workaround. For example:
SELECT @@GLOBAL.innodb_data_file_path;
61
62
Chapter 27 Extensions to SHOW Statements
Some extensions to SHOW statements accompany the implementation of INFORMATION_SCHEMA:
• SHOW can be used to get information about the structure of INFORMATION_SCHEMA itself.
• Several SHOW statements accept a WHERE clause that provides more flexibility in specifying which rows
to display.
INFORMATION_SCHEMA is an information database, so its name is included in the output from SHOW
DATABASES. Similarly, SHOW TABLES can be used with INFORMATION_SCHEMA to obtain a list of its
tables:
mysql> SHOW TABLES FROM INFORMATION_SCHEMA;
+---------------------------------------+
| Tables_in_INFORMATION_SCHEMA
|
+---------------------------------------+
| CHARACTER_SETS
|
| COLLATIONS
|
| COLLATION_CHARACTER_SET_APPLICABILITY |
| COLUMNS
|
| COLUMN_PRIVILEGES
|
| ENGINES
|
| EVENTS
|
| FILES
|
| GLOBAL_STATUS
|
| GLOBAL_VARIABLES
|
| KEY_COLUMN_USAGE
|
| PARTITIONS
|
| PLUGINS
|
| PROCESSLIST
|
| REFERENTIAL_CONSTRAINTS
|
| ROUTINES
|
| SCHEMATA
|
| SCHEMA_PRIVILEGES
|
| SESSION_STATUS
|
| SESSION_VARIABLES
|
| STATISTICS
|
| TABLES
|
| TABLE_CONSTRAINTS
|
| TABLE_PRIVILEGES
|
| TRIGGERS
|
| USER_PRIVILEGES
|
| VIEWS
|
+---------------------------------------+
SHOW COLUMNS and DESCRIBE can display information about the columns in individual
INFORMATION_SCHEMA tables.
SHOW statements that accept a LIKE clause to limit the rows displayed also permit a WHERE clause that
specifies more general conditions that selected rows must satisfy:
SHOW
SHOW
SHOW
SHOW
SHOW
SHOW
SHOW
SHOW
SHOW
CHARACTER SET
COLLATION
COLUMNS
DATABASES
FUNCTION STATUS
INDEX
OPEN TABLES
PROCEDURE STATUS
STATUS
63
SHOW
SHOW
SHOW
SHOW
TABLE STATUS
TABLES
TRIGGERS
VARIABLES
The WHERE clause, if present, is evaluated against the column names displayed by the SHOW statement.
For example, the SHOW CHARACTER SET statement produces these output columns:
mysql> SHOW CHARACTER SET;
+----------+-----------------------------+---------------------+--------+
| Charset | Description
| Default collation
| Maxlen |
+----------+-----------------------------+---------------------+--------+
| big5
| Big5 Traditional Chinese
| big5_chinese_ci
|
2 |
| dec8
| DEC West European
| dec8_swedish_ci
|
1 |
| cp850
| DOS West European
| cp850_general_ci
|
1 |
| hp8
| HP West European
| hp8_english_ci
|
1 |
| koi8r
| KOI8-R Relcom Russian
| koi8r_general_ci
|
1 |
| latin1
| cp1252 West European
| latin1_swedish_ci
|
1 |
| latin2
| ISO 8859-2 Central European | latin2_general_ci
|
1 |
...
To use a WHERE clause with SHOW CHARACTER SET, you would refer to those column names. As an
example, the following statement displays information about character sets for which the default collation
contains the string 'japanese':
mysql> SHOW CHARACTER SET WHERE `Default collation` LIKE '%japanese%';
+---------+---------------------------+---------------------+--------+
| Charset | Description
| Default collation
| Maxlen |
+---------+---------------------------+---------------------+--------+
| ujis
| EUC-JP Japanese
| ujis_japanese_ci
|
3 |
| sjis
| Shift-JIS Japanese
| sjis_japanese_ci
|
2 |
| cp932
| SJIS for Windows Japanese | cp932_japanese_ci
|
2 |
| eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci |
3 |
+---------+---------------------------+---------------------+--------+
This statement displays the multibyte character sets:
mysql> SHOW CHARACTER SET WHERE Maxlen > 1;
+---------+---------------------------+---------------------+--------+
| Charset | Description
| Default collation
| Maxlen |
+---------+---------------------------+---------------------+--------+
| big5
| Big5 Traditional Chinese | big5_chinese_ci
|
2 |
| ujis
| EUC-JP Japanese
| ujis_japanese_ci
|
3 |
| sjis
| Shift-JIS Japanese
| sjis_japanese_ci
|
2 |
| euckr
| EUC-KR Korean
| euckr_korean_ci
|
2 |
| gb2312 | GB2312 Simplified Chinese | gb2312_chinese_ci
|
2 |
| gbk
| GBK Simplified Chinese
| gbk_chinese_ci
|
2 |
| utf8
| UTF-8 Unicode
| utf8_general_ci
|
3 |
| ucs2
| UCS-2 Unicode
| ucs2_general_ci
|
2 |
| cp932
| SJIS for Windows Japanese | cp932_japanese_ci
|
2 |
| eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci |
3 |
+---------+---------------------------+---------------------+--------+
64
Chapter 28 MySQL 5.6 FAQ: INFORMATION_SCHEMA
Questions
• 28.1: Where can I find documentation for the MySQL INFORMATION_SCHEMA database?
• 28.2: Is there a discussion forum for INFORMATION_SCHEMA?
• 28.3: Where can I find the ANSI SQL 2003 specification for INFORMATION_SCHEMA?
• 28.4: What is the difference between the Oracle Data Dictionary and MySQL INFORMATION_SCHEMA?
• 28.5: Can I add to or otherwise modify the tables found in the INFORMATION_SCHEMA database?
Questions and Answers
28.1: Where can I find documentation for the MySQL INFORMATION_SCHEMA database?
See Chapter 1, INFORMATION_SCHEMA Tables
28.2: Is there a discussion forum for INFORMATION_SCHEMA?
See http://forums.mysql.com/list.php?101.
28.3: Where can I find the ANSI SQL 2003 specification for INFORMATION_SCHEMA?
Unfortunately, the official specifications are not freely available. (ANSI makes them available for purchase.)
However, there are books available, such as SQL-99 Complete, Really by Peter Gulutzan and Trudy
Pelzer, that provide a comprehensive overview of the standard, including INFORMATION_SCHEMA.
28.4: What is the difference between the Oracle Data Dictionary and MySQL
INFORMATION_SCHEMA?
Both Oracle and MySQL provide metadata in tables. However, Oracle and MySQL use different table
names and column names. The MySQL implementation is more similar to those found in DB2 and SQL
Server, which also support INFORMATION_SCHEMA as defined in the SQL standard.
28.5: Can I add to or otherwise modify the tables found in the INFORMATION_SCHEMA database?
No. Since applications may rely on a certain standard structure, this should not be modified. For this
reason, we cannot support bugs or other issues which result from modifying INFORMATION_SCHEMA
tables or data.
65
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