You can use a SIGNAL statement to raise an errorcondition if the business rule defined in your trigger is violated.
如果违反了您在触发器中定义的业务规则,就可以使用signal语句来抛出一个错误条件信号。
2
In the case of the DB2 example in the left column of Table 3, if a particular SQL statement fails and generates an error, control is passed to the condition handler.