For DELETE operations, the return value should be OLD.The return value of a row-level trigger fired AFTER or a statement-level trigger fired BEFORE or AFTERis always ignored; it might as well be null. However, any of these types of triggers might still abort the entire operation by raisin...
触发事件:即在何种情况下触发Trigger;例如:insert,update,delete。 触发时间:即在Trigger是在触发时间发生之前(before)还是之后(after)触发,也就是触发事件和该trigger的操作顺序。 触发器本身:即该trigger被触发后的目的和意图,正是触发器本身要做的事情。例如:pl/sql块。 触发频率:说明触发器内定义的动作被执行的...
在本章中,无涯教程将讨论PL/SQL中的触发器,触发器是存储的程序,在发生某些事件时会自动执行或触发。 创建触发器 创建触发器的语法是- CREATE [OR REPLACE ] TRIGGER trigger_name {BEFORE | AFTER | INSTEAD OF } {INSERT [OR] | UPDATE [OR] | DELETE} [OF col_name] ON table_name [REFERENCING OLD...
PL/SQL Triggers A trigger is a PL/SQL block which will run automatically whenever an event occurs. PL/SQL block may be associated with a table, a view or to a database. A trigger is a procedure that is triggered automatically when on the table that is created is executed a command ...
数据服务器能够对 PL/SQL 触发器定义进行编译。这些示例帮助您创建有效的触发器以及诊断 PL/SQL 触发器编译错误。 行级前触发器 以下示例演示行级别的前触发器,对于每个隶属于部门 30 的新职员,在将该职员的记录插入到 EMP 表之前,此触发器计算该职员的佣金: CREATE OR REPLACE TRIGGER emp_comm_trig BEFORE ...
当上述代码在SQL提示符执行时,它产生了以下结果: Trigger created. 1. 这里以下两点是重要的,应小心注意: OLD和NEW引用是不可用于表级触发器,而不可以使用它们的创纪录级别的触发器。 如果想查询表中相同的触发,那么应用应该使用AFTER关键字,因为触发器可以查询该表,或再次改变它最初的变化仅适用后的表是回到一致...
DELETEFROMMEDICAL_BILLSWHEREbill_id=1;DELETEFROMMEDICAL_BILLSWHEREbill_id=3; 1.5 Display the data again. select*fromMEDICAL_BILLS; select*fromMEDICAL_BILLS_HISTORY; References Creating a DML Trigger: Examples PL/SQL Triggers :- Oracle official docs Oracle PL/SQL – Before DELETE Trigger example...
PL/SQL - Triggers - In this chapter, we will discuss Triggers in PL/SQL. Triggers are stored programs, which are automatically executed or fired when some events occur. Triggers are, in fact, written to be executed in response to any of the following eve
select*fromBANK_TRANSACTIONS;Copy select*fromBANK_TRANSACTIONS_AUDIT;Copy References Oracle – CREATE TRIGGER Statement Oracle – PL/SQL Triggers CategoriesoracleTagsbefore update,oracle,plsql,trigger
CREATE[OR REPLACE]TRIGGERtrigger_name {BEFORE|AFTER} {DELETE|INSERT|UPDATE[OF 列名]} -- 触发条件具体到某一列ON表名[FOR EACH ROW [WHEN (条件)]) -- 表示行级触发器, 省略则为语句触发器 PLSQL块 实例1: 禁止在休息日(周六、周日)改变emp表的数据。