WHEN 子句和触发器(Trigger)动作可能访问使用表单NEW.column-name和OLD.column-name的引用插入、删除或更新的行元素,其中 column-name 是从与触发器关联的表的列的名称。 如果提供 WHEN 子句,则只针对 WHEN 子句为真的指定行执行 SQL 语句。如果没有提供 WHEN 子句,则针对所有行执行 SQL 语句。 BEFORE 或 AFTER...
Triggers can contain PL/SQL code and SQL code that are executed as a block. The trigger can be invoked either before or after the execution of the order insert, update, or delete. Triggers can be: –Trigger for the application: this type of trigger is run when an event occurs in an...
Triggers are commonly used to perform auditing actions, to maintain table integrity in place of native constraints such as foreign keys and check constraints, and to perform other post DML processing. Triggers operate under the scope of a transaction so if a table were updated, for instance, t...
Triggers can be used for performing tasks that can’t be done using the point-and-click tools that are in the Salesforce UI. Triggers can be defined for top-level standard objects, such as account, contact, custom objects, and some standard child objects. When triggers are created, they...
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*FROMaudits;Code language:PostgreSQL SQL dialect and PL/pgSQL(pgsql) The output showed that a new row had been inserted. It means that theDELETEaction fired the triggercustomer_audit_trg. In this tutorial, you have learned about Oracle triggers and how to create new triggers using the...
Within this sql trigger tutorial, you will findCreate Triggerin SQL Server script, where you can use the syntax in any SQL Server version. In thisSQL Server triggerexample, the aim of thesql triggeris to keep history of changes on price column in a table. ...
Article Overview In this article, we will learn how to drop, alter, enable, and disable a PostgreSQL trigger. In the 1st part of this series, we got an
This Oracle tutorial explains how to create a BEFORE UPDATE Trigger in Oracle with syntax and examples. A BEFORE UPDATE Trigger means that Oracle will fire this trigger before the UPDATE operation is executed.
One of the most used scenarios for triggers is to maintain a log of changes in a given table. In such case, there is no point on having three different triggers, each one firing on INSERT, UPDATE and DELETE operations. Fortunately we have the chance to use one single trigger for all ...