information_schema系统表——TRIGGERS

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本文介绍了MySQL中TRIGGERS表的详细信息，包括触发器的相关属性如触发时机、操作类型等，并通过一个实例展示了如何使用INFORMATION_SCHEMA.TRIGGERS来查看特定数据库中的触发器详情。

触发器

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	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`
`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`	`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 Section 13.7.5.38, “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 Section 23.3, “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.
ACTION_ORDER: The ordinal position of the trigger's action within the list of triggers on the same table with the same EVENT_MANIPULATION and ACTION_TIMING values. Before MySQL 5.7.2, this value is always 0 because it is not possible for a table to have more than one trigger with the same EVENT_MANIPULATION and ACTION_TIMINGvalues.
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_ROWalways contains the value 'OLD' and ACTION_REFERENCE_NEW_ROW always contains the value 'NEW'.
CREATED: The date and time when the trigger was created. This is a TIMESTAMP(2) value (with a fractional part in hundredths of seconds) for triggers created in MySQL 5.7.2 or later, NULL for triggers created prior to 5.7.2.
SQL_MODE: The SQL mode in effect when the trigger was created, and under which the trigger executes. For the permitted values, see Section 5.1.8, “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, and ACTION_REFERENCE_NEW_TABLE.

Example, using the ins_sum trigger defined in Section 23.3, “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: 1
          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: 2013-07-05 07:41:21.26
                  SQL_MODE: NO_ENGINE_SUBSTITUTION
                   DEFINER: me@localhost
      CHARACTER_SET_CLIENT: utf8
      COLLATION_CONNECTION: utf8_general_ci
        DATABASE_COLLATION: latin1_swedish_ci