PLSQL:NEW和:OLD [英] PLSQL :NEW and :OLD

问题描述

谁能帮助我了解何时在PLSQL块中使用:NEW和:OLD，我发现很难理解它们的用法.

Can anyone help me understand when to use :NEW and :OLD in PLSQL blocks, I'm finding it very difficult to understand their usage.

推荐答案

您通常在

You normally use the terms in a trigger using :old to reference the old value and :new to reference the new value.

这是上面链接的Oracle文档中的一个示例

Here is an example from the Oracle documentation linked to above

CREATE OR REPLACE TRIGGER Print_salary_changes
  BEFORE DELETE OR INSERT OR UPDATE ON Emp_tab
  FOR EACH ROW
WHEN (new.Empno > 0)
DECLARE
    sal_diff number;
BEGIN
    sal_diff  := :new.sal  - :old.sal;
    dbms_output.put('Old salary: ' || :old.sal);
    dbms_output.put('  New salary: ' || :new.sal);
    dbms_output.put_line('  Difference ' || sal_diff);
END;

在此示例中，触发器触发BEFORE DELETE OR INSERT OR UPDATE :old.sal将包含触发触发器之前的薪水，而:new.sal将包含新值.

In this example the trigger fires BEFORE DELETE OR INSERT OR UPDATE :old.sal will contain the salary prior to the trigger firing and :new.sal will contain the new value.

这篇关于PLSQL:NEW和:OLD的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！