触发器创建及Navicat中使用

　　mysql中的触发器（trigger）使用

　Trigger：

　　示例：

mysql> CREATE TABLE account (acct_num INT, amount DECIMAL(10,2));
Query OK, 0 rows affected (0.03 sec)

mysql> CREATE TRIGGER ins_sum BEFORE INSERT ON account
    -> FOR EACH ROW SET @sum = @sum + NEW.amount;
Query OK, 0 rows affected (0.06 sec)

　　解析：<原谅我这懒惰的搬运工>

　　　The CREATE TRIGGER statement creates a trigger named ins_sum that is associated with the account table. It also includes clauses that specify the trigger action time, the triggering event, and what to do when the trigger activates:

• The keyword BEFORE indicates the trigger action time. In this case, the trigger activates before each row inserted into the table. The other permitted keyword here is AFTER.
• The keyword INSERT indicates the trigger event; that is, the type of operation that activates the trigger. In the example, INSERT operations cause trigger activation. You can also create triggers for DELETE and UPDATE operations.
• The statement following FOR EACH ROW defines the trigger body; that is, the statement to execute each time the trigger activates, which occurs once for each row affected by the triggering event. In the example, the trigger body is a simple SET that accumulates into a user variable the values inserted into the amount column. The statement refers to the column as NEW.amount which means “the value of theamount column to be inserted into the new row.”

　　具体参见：http://dev.mysql.com/doc/refman/5.7/en/trigger-syntax.html

　　Navicat中使用

　　1.选中要添加触发器的表；

　　  2.打开其设计表；

　　  3.打开触发器，在指定栏中设置触发器；

　　　具体参见：http://blog.csdn.net/cqnuztq/article/details/9735245