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如果我們銷毀與其關(guān)聯(lián)的表，觸發(fā)器也會(huì)被銷毀。這稱為觸發(fā)器的顯式銷毀。可以通過一個(gè)例子來理解 –

示例

假設(shè)我們?cè)诿麨椤癝ample”的表上有一個(gè)名為“trigger_before_delete_sample”的觸發(fā)器。現(xiàn)在，如果我們刪除該表，那么與該表關(guān)聯(lián)的上述觸發(fā)器也將被刪除。

mysql> Show Triggers\G
*************************** 1. row ***************************
              Trigger: trigger_before_delete_sample
                Event: DELETE
                Table: sample
            Statement: BEGIN
         SET @count = if (@count IS NULL, 1, (@count+1));
         INSERT INTO sample_rowaffected values (@count);
END
               Timing: BEFORE
              Created: 2017-11-21 12:31:58.70
             sql_mode: ONLY_FULL_GROUP_BY,
                       STRICT_TRANS_TABLES,
                       NO_ZERO_IN_DATE,
                       NO_ZERO_DATE,
                       ERROR_FOR_DIVISION_BY_ZERO,
                       NO_AUTO_CREATE_USER,
                       NO_ENGINE_SUBSTITUTION
              Definer: root@localhost
 character_set_client: cp850
 collation_connection: cp850_general_ci
   Database Collation: latin1_swedish_ci
*************************** 2. row ***************************
              Trigger: before_inser_studentage
                Event: INSERT
                Table: student_age
            Statement: IF NEW.age < 0 THEN SET NEW.age = 0;
END IF
               Timing: BEFORE
              Created: 2017-11-21 11:26:15.34
             sql_mode: ONLY_FULL_GROUP_BY,
                       STRICT_TRANS_TABLES,
                       NO_ZERO_IN_DATE,
                       NO_ZERO_DATE,
                       ERROR_FOR_DIVISION_BY_ZERO,
                       NO_AUTO_CREATE_USER,
                       NO_ENGINE_SUBSTITUTION
              Definer: root@localhost
 character_set_client: cp850
 collation_connection: cp850_general_ci
   Database Collation: latin1_swedish_ci
2 rows in set (0.01 sec)

登錄后復(fù)制

上面的結(jié)果集顯示數(shù)據(jù)庫中有兩個(gè)觸發(fā)器，其中一個(gè)觸發(fā)器與名為“Sample”的表關(guān)聯(lián)。現(xiàn)在，借助以下語句，我們將刪除該表 –

mysql> DROP table sample;
Query OK, 0 rows affected (0.26 sec)

登錄后復(fù)制

現(xiàn)在借助以下語句，我們可以看到與名為“Sample”的表關(guān)聯(lián)的觸發(fā)器也被銷毀了。

mysql> Show Triggers\G
*************************** 1. row ***************************
              Trigger: before_inser_studentage
                Event: INSERT
                Table: student_age
            Statement: IF NEW.age < 0 THEN SET NEW.age = 0;
END IF
               Timing: BEFORE
              Created: 2017-11-21 11:26:15.34
             sql_mode: ONLY_FULL_GROUP_BY,
                       STRICT_TRANS_TABLES,
                       NO_ZERO_IN_DATE,
                       NO_ZERO_DATE,
                       ERROR_FOR_DIVISION_BY_ZERO,
                       NO_AUTO_CREATE_USER,
                       NO_ENGINE_SUBSTITUTION
              Definer: root@localhost
 character_set_client: cp850
 collation_connection: cp850_general_ci
   Database Collation: latin1_swedish_ci
1 row in set (0.01 sec)

登錄后復(fù)制

以上就是當(dāng)我們刪除具有該觸發(fā)器的表時(shí)，觸發(fā)器會(huì)發(fā)生什么情況？的詳細(xì)內(nèi)容，更多請(qǐng)關(guān)注www.92cms.cn其它相關(guān)文章！