Table of Contents
INFORMATION_SCHEMA SCHEMATA TableINFORMATION_SCHEMA TABLES TableINFORMATION_SCHEMA COLUMNS TableINFORMATION_SCHEMA STATISTICS TableINFORMATION_SCHEMA USER_PRIVILEGES TableINFORMATION_SCHEMA SCHEMA_PRIVILEGES TableINFORMATION_SCHEMA TABLE_PRIVILEGES TableINFORMATION_SCHEMA COLUMN_PRIVILEGES TableINFORMATION_SCHEMA CHARACTER_SETS TableINFORMATION_SCHEMA COLLATIONS TableINFORMATION_SCHEMA
COLLATION_CHARACTER_SET_APPLICABILITY TableINFORMATION_SCHEMA TABLE_CONSTRAINTS TableINFORMATION_SCHEMA KEY_COLUMN_USAGE TableINFORMATION_SCHEMA ROUTINES TableINFORMATION_SCHEMA VIEWS TableINFORMATION_SCHEMA TRIGGERS TableINFORMATION_SCHEMA PLUGINS TableINFORMATION_SCHEMA ENGINES TableINFORMATION_SCHEMA PARTITIONS TableINFORMATION_SCHEMA EVENTS TableINFORMATION_SCHEMA FILES TableINFORMATION_SCHEMA TABLESPACES TableINFORMATION_SCHEMA PROCESSLIST TableINFORMATION_SCHEMA REFERENTIAL_CONSTRAINTS TableINFORMATION_SCHEMA GLOBAL_STATUS and
SESSION_STATUS
TablesINFORMATION_SCHEMA GLOBAL_VARIABLES and
SESSION_VARIABLES
TablesINFORMATION_SCHEMA PARAMETERS TableINFORMATION_SCHEMA PROFILING TableINFORMATION_SCHEMA TablesSHOW Statements
INFORMATION_SCHEMA provides access to database
metadata.
Metadata is data about the data, such as the name of a database or table, the data type of a column, or access privileges. Other terms that sometimes are used for this information are data dictionary and system catalog.
INFORMATION_SCHEMA is the information database,
the place that stores information about all the other databases that
the MySQL server maintains. Inside
INFORMATION_SCHEMA there are several read-only
tables. They are actually views, not base tables, so there are no
files associated with them.
In effect, we have a database named
INFORMATION_SCHEMA, although the server does not
create a database directory with that name. It is possible to select
INFORMATION_SCHEMA as the default database with a
USE statement, but it is possible
only to read the contents of tables. You cannot insert into them,
update them, or delete from them.
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 DESC;+------------+------------+--------+ | table_name | table_type | engine | +------------+------------+--------+ | v56 | VIEW | NULL | | v3 | VIEW | NULL | | v2 | VIEW | NULL | | v | VIEW | NULL | | tables | BASE TABLE | MyISAM | | t7 | BASE TABLE | MyISAM | | t3 | BASE TABLE | MyISAM | | t2 | BASE TABLE | MyISAM | | t | BASE TABLE | MyISAM | | pk | BASE TABLE | InnoDB | | loop | BASE TABLE | MyISAM | | kurs | BASE TABLE | MyISAM | | k | BASE TABLE | MyISAM | | into | BASE TABLE | MyISAM | | goto | BASE TABLE | MyISAM | | fk2 | BASE TABLE | InnoDB | | fk | BASE TABLE | InnoDB | +------------+------------+--------+ 17 rows in set (0.01 sec)
Explanation: The statement requests a list of all the tables in
database db5, in reverse alphabetical order,
showing just three pieces of information: the name of the table, its
type, and its storage engine.
The definition for character columns (for example,
TABLES.TABLE_NAME) is generally
VARCHAR( where N) CHARACTER SET
utf8N 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. However,
searches in INFORMATION_SCHEMA string columns are
also affected by file system case sensitivity. For more information,
see Section 9.1.7.8, “Collation and INFORMATION_SCHEMA Searches”.
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 will see
NULL.
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. That is, all access is done on tables.
Nobody needs to learn a new statement syntax. Because they
already know how SELECT works,
they only need to learn the object names.
The implementor need not worry about adding keywords.
There are millions of possible output variations, instead of just one. This provides more flexibility for applications that have varying requirements about what metadata they need.
Migration is easier because every other DBMS does it this way.
However, because SHOW is popular and
because it might be confusing were it to disappear, the advantages
of conventional syntax are not a sufficient reason to eliminate
SHOW. In fact, along with the
implementation of INFORMATION_SCHEMA, there are
enhancements to SHOW as well. These
are described in Section 19.30, “Extensions to SHOW Statements”.
There is no difference between the privileges required for
SHOW statements and those required to
select information from INFORMATION_SCHEMA. In
either case, you have to have some privilege on an object in order
to see information about it.
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
EXPLAIN output that is specific to
interpreting the cost of INFORMATION_SCHEMA
queries, see Section 7.2.21, “INFORMATION_SCHEMA Optimization”.
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.
The following sections describe each of the tables and columns that
are 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.
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:
http://web.archive.org/web/20070409075643rn_1/www.dbazine.com/db2/db2-disarticles/gulutzan5.
Each section indicates what SHOW
statement is equivalent to a SELECT
that retrieves information from
INFORMATION_SCHEMA, if there is such a statement.
For SHOW statements that display
information for the default database if you omit a FROM
clause, you can often
select information for the default database by adding an
db_nameAND TABLE_SCHEMA = CURRENT_SCHEMA() condition to
the WHERE clause of a query that retrieves
information from an INFORMATION_SCHEMA table.
At present, there are some missing columns and some columns out of order. We are working on this and updating the documentation as changes are made.
For answers to questions that are often asked concerning the
INFORMATION_SCHEMA database, see
Section A.7, “MySQL 5.5 FAQ — INFORMATION_SCHEMA”.
A schema is a database, so the
SCHEMATA table provides information
about databases.
INFORMATION_SCHEMA
Name | SHOW
Name | Remarks |
CATALOG_NAME | def | |
SCHEMA_NAME | 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']
The TABLES table provides information
about tables in databases.
INFORMATION_SCHEMA
Name | SHOW
Name | Remarks |
TABLE_CATALOG | 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 |
Notes:
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. Currently, 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.
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 FROMdb_name[LIKE 'wild']
The COLUMNS table provides
information about columns in tables.
INFORMATION_SCHEMA
Name | SHOW
Name | Remarks |
TABLE_CATALOG | def | |
TABLE_SCHEMA | ||
TABLE_NAME | ||
COLUMN_NAME | Field | |
ORDINAL_POSITION | see notes | |
COLUMN_DEFAULT | Default | |
IS_NULLABLE | Null | |
DATA_TYPE | Type | |
CHARACTER_MAXIMUM_LENGTH | Type | |
CHARACTER_OCTET_LENGTH | ||
NUMERIC_PRECISION | Type | |
NUMERIC_SCALE | 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
multi-byte 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.
The following statements are nearly equivalent:
SELECT COLUMN_NAME, DATA_TYPE, IS_NULLABLE, COLUMN_DEFAULT FROM INFORMATION_SCHEMA.COLUMNS WHERE table_name = 'tbl_name' [AND table_schema = 'db_name'] [AND column_name LIKE 'wild'] SHOW COLUMNS FROMtbl_name[FROMdb_name] [LIKE 'wild']
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 | |
INDEX_SCHEMA | = Database | |
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 FROMtbl_nameFROMdb_name
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 | '
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.
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 | '
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.
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 | '
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 ...
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 | '
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 ...
The CHARACTER_SETS table provides
information about available character sets.
INFORMATION_SCHEMA
Name | SHOW
Name | Remarks |
CHARACTER_SET_NAME | Charset | |
DEFAULT_COLLATE_NAME | Default collation | |
DESCRIPION | 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']
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']
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 | Remarks |
COLLATION_NAME | Collation | |
CHARACTER_SET_NAME | Charset |
The TABLE_CONSTRAINTS table describes
which tables have constraints.
INFORMATION_SCHEMA
Name | SHOW
Name | Remarks |
CONSTRAINT_CATALOG | 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.
The KEY_COLUMN_USAGE table describes
which key columns have constraints.
INFORMATION_SCHEMA
Name | SHOW
Name | Remarks |
CONSTRAINT_CATALOG | 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.
One row with CONSTRAINT_NAME =
'CO', TABLE_NAME =
't3', COLUMN_NAME =
's2',
ORDINAL_POSITION =
1,
POSITION_IN_UNIQUE_CONSTRAINT =
1.
The ROUTINES table provides
information about stored routines (both procedures and functions).
The ROUTINES table does not include
user-defined functions (UDFs) at this time.
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 | Remarks |
SPECIFIC_NAME | specific_name | |
ROUTINE_CATALOG | 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 | |
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 | |
EXTERNAL_NAME | NULL | |
EXTERNAL_LANGUAGE | language | NULL |
PARAMETER_STYLE | 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:
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.
CHARACTER_SET_CLIENT is the session value
of the character_set_client
system variable when the routine was created.
COLLATION_CONNECTION is the session value
of the collation_connection
system variable when the routine was created.
DATABASE_COLLATION is the collation of the
database with which the routine is associated.
The DATA_TYPE,
CHARACTER_MAXIMUM_LENGTH,
CHARACTER_OCTET_LENGTH,
NUMERIC_PRECISION,
NUMERIC_SCALE,
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.
These columns were added in MySQL 5.5.3.
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.
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 | Remarks |
TABLE_CATALOG | 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 the 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
Section 12.1.16, “CREATE VIEW Syntax”.)
The DEFINER column indicates who defined
the view. SECURITY_TYPE has a value of
DEFINER or INVOKER.
CHARACTER_SET_CLIENT is the session value
of the character_set_client
system variable when the view was created.
COLLATION_CONNECTION is the session value
of the collation_connection
system variable when the view was created.
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.
The TRIGGERS table provides
information about triggers. You must have the
TRIGGER privilege to access this
table.
INFORMATION_SCHEMA
Name | SHOW
Name | Remarks |
TRIGGER_CATALOG | 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 | ROW | |
ACTION_TIMING | Timing | |
ACTION_REFERENCE_OLD_TABLE | NULL | |
ACTION_REFERENCE_NEW_TABLE | NULL | |
ACTION_REFERENCE_OLD_ROW | OLD | |
ACTION_REFERENCE_NEW_ROW | NEW | |
CREATED | NULL (0) | |
SQL_MODE | MySQL extension | |
DEFINER | MySQL extension | |
CHARACTER_SET_CLIENT | MySQL extension | |
COLLATION_CONNECTION | MySQL extension | |
DATABASE_COLLATION | MySQL extension |
Notes:
The TRIGGER_SCHEMA and
TRIGGER_NAME columns contain the name of
the database in which the trigger occurs and the trigger name,
respectively.
The EVENT_MANIPULATION column contains one
of the values 'INSERT',
'DELETE', or 'UPDATE'.
As noted in Section 18.3, “Using Triggers”, every trigger is
associated with exactly one table. The
EVENT_OBJECT_SCHEMA and
EVENT_OBJECT_TABLE columns contain the
database in which this table occurs, and the table's name.
The ACTION_ORDER statement contains the
ordinal position of the trigger's action within the list of
all similar triggers on the same table. Currently, 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.
The ACTION_STATEMENT column contains the
statement to be executed when the trigger is invoked. This is
the same as the text displayed in the
Statement column of the output from
SHOW TRIGGERS. Note that this
text uses UTF-8 encoding.
The ACTION_ORIENTATION column always
contains the value 'ROW'.
The ACTION_TIMING column contains one of
the two values 'BEFORE' or
'AFTER'.
The columns ACTION_REFERENCE_OLD_ROW and
ACTION_REFERENCE_NEW_ROW contain 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'.
The SQL_MODE column shows the server SQL
mode that was in effect at the time when the trigger was
created (and thus which remains in effect for this trigger
whenever it is invoked, regardless of the current
server SQL mode). The possible range of values for
this column is the same as that of the
sql_mode system variable. See
Section 5.1.8, “Server SQL Modes”.
The DEFINER column indicates who defined
the trigger.
CHARACTER_SET_CLIENT is the session value
of the character_set_client
system variable when the trigger was created.
COLLATION_CONNECTION is the session value
of the collation_connection
system variable when the trigger was created.
DATABASE_COLLATION is 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
Section 18.3, “Using Triggers”:
mysql> SELECT * FROM INFORMATION_SCHEMA.TRIGGERS\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:
DEFINER: me@localhost
The PLUGINS table provides
information about server plugins.
INFORMATION_SCHEMA
Name | SHOW
Name | Remarks |
PLUGIN_NAME | Name | MySQL extension |
PLUGIN_VERSION | MySQL extension | |
PLUGIN_STATUS | Status | MySQL extension |
PLUGIN_TYPE | Type | MySQL extension |
PLUGIN_TYPE_VERSION | MySQL extension | |
PLUGIN_LIBRARY | Library | MySQL extension |
PLUGIN_LIBRARY_VERSION | MySQL extension | |
PLUGIN_AUTHOR | MySQL extension | |
PLUGIN_DESCRIPTION | MySQL extension | |
PLUGIN_LICENSE | MySQL extension |
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 or
INFORMATION_SCHEMA.
PLUGIN_TYPE_VERSION is the version from the
plugin's type-specific descriptor.
PLUGIN_LIBRARY is the name of the plugin
shared object 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.
For plugins installed with INSTALL
PLUGIN, the PLUGIN_NAME and
PLUGIN_LIBARY values are also registered in the
mysql.plugin table.
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 Section 22.2, “The MySQL Plugin Interface”.
Plugin information is also available using the
SHOW PLUGINS statement. See
Section 12.5.5.26, “SHOW PLUGINS Syntax”.
The PLUGINS 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.
See also Section 12.5.5.17, “SHOW ENGINES Syntax”.
The PARTITIONS table provides
information about table partitions. See
Chapter 17, 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.
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
Section 17.2, “Partition 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
Section 17.2.6, “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.
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.
UPDATE_TIME: The time that the partition or
subpartition was last modified.
CHECK_TIME: The last time that the table to
which this partition or subpartition belongs was checked.
Some storage engines do not update this time; for tables
using these storage engines, this value 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.
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 MySQL Cluster
tables; otherwise the value of this column is always
0.
TABLESPACE_NAME: This column contains the
name of tablespace to which the partition belongs. In MySQL
5.5, 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.)
The EVENTS table provides information
about scheduled events, which are discussed in
Section 18.4, “Using the Event Scheduler”. The SHOW Name values
correspond to column names of the SHOW
EVENTS statement.
INFORMATION_SCHEMA
Name | SHOW
Name | Remarks |
EVENT_CATALOG | def, MySQL extension | |
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 |
SQL_MODE | MySQL extension | |
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
'
format.
user_name'@'host_name'
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.
EVENT_BODY: The language used for the
statements in the event's DO
clause; in MySQL 5.5, 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 at the
time the event was created or altered.
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
Section 16.4.1.8, “Replication of Invoked Features”, for more
information.
ON_COMPLETION: One of the two values
PRESERVE or NOT
PRESERVE.
CREATED: The date and time when the event
was created. This is a DATETIME
value.
LAST_ALTERED: The date and time when the
event was last modified. This is a
DATETIME 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 is the session value
of the character_set_client
system variable when the event was created.
COLLATION_CONNECTION is the session value
of the collation_connection
system variable when the event was created.
DATABASE_COLLATION is the collation of the
database with which the event is associated.
Example: Suppose 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
ENABLED;
(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: paul@localhost TIME_ZONE: SYSTEM EVENT_BODY: SQL EVENT_DEFINITION: BEGIN 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 Section 18.4.4, “Event Metadata”.
See also Section 12.5.5.19, “SHOW EVENTS Syntax”.
The FILES table provides information
about the files in which MySQL tablespace data is stored.
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 | |
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 a data file
created by CREATE TABLESPACE or
ALTER TABLESPACE.
FILE_TYPE is the tablespace file type.
TABLESPACE_NAME is the name of the
tablespace with which the file is associated.
Currently, the value of the
TABLESPACE_CATALOG column is always
NULL.
TABLE_NAME is the name of the table with
which the file is associated, if any.
The EXTENT_SIZE is always
0.
The TABLESPACES table provides
information about active tablespaces. The table was added in MySQL
5.5.3.
INFORMATION_SCHEMA
Name | SHOW
Name | Remarks |
TABLESPACE_NAME | MySQL extension | |
ENGINE | MySQL extension | |
TABLESPACE_TYPE | MySQL extension | |
LOGFILE_GROUP_NAME | MySQL extension | |
EXTENT_SIZE | MySQL extension | |
AUTOEXTEND_SIZE | MySQL extension | |
MAXIMUM_SIZE | MySQL extension | |
NODEGROUP_ID | MySQL extension | |
TABLESPACE_COMMENT | MySQL extension |
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
Section 12.5.5.30, “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,
then MySQL will populate 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.
The following statements are equivalent:
SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST SHOW FULL PROCESSLIST
The REFERENTIAL_CONSTRAINTS table
provides information about foreign keys.
INFORMATION_SCHEMA
Name | SHOW
Name | Remarks |
| CONSTRAINT_CATALOG | 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.
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 Section 12.5.5.36, “SHOW STATUS Syntax”).
INFORMATION_SCHEMA
Name | SHOW
Name | Remarks |
| VARIABLE_NAME | Variable_name | |
| VARIABLE_VALUE | Value |
Notes:
The VARIABLE_VALUE column for each of these
tables is defined as VARCHAR(20480).
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
Section 12.5.5.40, “SHOW VARIABLES Syntax”).
INFORMATION_SCHEMA
Name | SHOW
Name | Remarks |
| VARIABLE_NAME | Variable_name | |
| VARIABLE_VALUE | Value |
Notes:
The VARIABLE_VALUE column for each of these
tables is defined as VARCHAR(20480).
The PARAMETERS table provides
information about stored function and procedure parameters, and
about return values for stored functions. Parameter information is
similar to the contents of the param_list
column in the mysql.proc table.
INFORMATION_SCHEMA
Name | mysql.proc Name | Remarks |
SPECIFIC_CATALOG | def | |
SPECIFIC_SCHEMA | db | routine database |
SPECIFIC_NAME | name | routine name |
ORDINAL_POSITION | 1, 2, 3, ... for parameters, 0 for function RETURNS
clause | |
PARAMETER_MODE | IN, OUT, INOUT
(NULL for RETURNS) | |
PARAMETER_NAME | parameter name (NULL for RETURNS) | |
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 | |
CHARACTER_SET_NAME | same as for COLUMNS table | |
COLLATION_NAME | same as for COLUMNS table | |
DTD_IDENTIFIER | same as for COLUMNS table | |
ROUTINE_TYPE | type | same as for ROUTINES table |
Notes:
The PARAMETERS table was added in
MySQL 5.5.3.
For successive parameters of a stored function or procedure,
the ORDINAL_POSITION values are 1, 2, 3,
and so forth. For a stored function, there is also a row that
describes the data type for the RETURNS
clause. The return value is not a true parameter, so the row
that describes it has these unique characteristics:
The ORDINAL_POSITION value is 0.
The PARAMETER_NAME and
PARAMETER_MODE values are
NULL because the return value has no
name and the mode does not apply.
The ROUTINE_TYPE column was added in MySQL
6.0.5. (Bug#33106)
The PROFILING table provides
statement profiling information. Its contents correspond to the
information produced by the SHOW
PROFILES and SHOW PROFILE
statements (see Section 12.5.5.32, “SHOW PROFILES Syntax”). The table is
empty unless the profiling
session variable is set to 1.
INFORMATION_SCHEMA
Name | SHOW
Name | Remarks |
QUERY_ID | Query_ID | |
SEQ | | |
STATE | Status | |
DURATION | Duration | |
CPU_USER | CPU_user | |
CPU_SYSTEM | CPU_system | |
CONTEXT_VOLUNTARY | Context_voluntary | |
CONTEXT_INVOLUNTARY | Context_involuntary | |
BLOCK_OPS_IN | Block_ops_in | |
BLOCK_OPS_OUT | Block_ops_out | |
MESSAGES_SENT | Messages_sent | |
MESSAGES_RECEIVED | Messages_received | |
PAGE_FAULTS_MAJOR | Page_faults_major | |
PAGE_FAULTS_MINOR | Page_faults_minor | |
SWAPS | Swaps | |
SOURCE_FUNCTION | Source_function | |
SOURCE_FILE | Source_file | |
SOURCE_LINE | Source_line |
Notes:
QUERY_ID is a numeric statement identifier.
SEQ is a sequence number indicating the
display order for rows with the same
QUERY_ID value.
STATE is the profiling state to which the
row measurements apply.
DURATION indicates how long statement
execution remained in the given state, in seconds.
CPU_USER and CPU_SYSTEM
indicate user and system CPU use, in seconds.
CONTEXT_VOLUNTARY and
CONTEXT_INVOLUNTARY indicate how many
voluntary and involuntary context switches occurred.
BLOCK_OPS_IN and
BLOCK_OPS_OUT indicate the number of block
input and output operations.
MESSAGES_SENT and
MESSAGES_RECEIVED indicate the number of
communication messages sent and received.
PAGE_FAULTS_MAJOR and
PAGE_FAULTS_MINOR indicate the number of
major and minor page faults.
SWAPS indicates how many swaps occurred.
SOURCE_FUNCTION,
SOURCE_FILE, and
SOURCE_LINE provide information indicating
where in the source code the profiled state executes.
Some extensions to SHOW statements
accompany the implementation of
INFORMATION_SCHEMA:
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 |
+---------------------------------------+
27 rows in set (0.00 sec)
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 allow a WHERE clause that
enables specification of more general conditions that selected
rows must satisfy:
SHOW CHARACTER SET SHOW COLLATION SHOW COLUMNS SHOW DATABASES SHOW FUNCTION STATUS SHOW INDEX SHOW OPEN TABLES SHOW PROCEDURE STATUS SHOW STATUS SHOW TABLE STATUS SHOW TABLES SHOW TRIGGERS SHOW 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 multi-byte 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 |
+---------+---------------------------+---------------------+--------+