ORACLE_TRIGGER

Posted 2020-10-15 yjhsbn

PL/SQL TRIGGER Statement

PL/SQL TRIGGER  Statement

The trigger statemet is a especially stored procedure.It define some event about database(such as,INSERT,UPDATE,CREATE and so on).When the special database event occur and execute the corresponse FUNCTION BLOCK. 

TRIGGER Syntax:

create or replace trigger tri_name

[befor|after|instead of] tri_event

on table_naem|view_name|db_name

[for each row] [when tri_condition]

begin

　　plsql_sentences;

end tri_name;

 Demo Database:

Step one:Create a table to record information for TRIGGER operator.

Create TABLE dept_log(
        operate_tag VARCHAR2(10),
        operate_time DATE
        
);

 

Step two:Create a trigger on table dept.

CREATE OR REPLACE TRIGGER tri_dept
       BEFORE INSERT
       ON dept
DECLARE 
       var_tag VARCHAR2(10);
BEGIN
       IF inserting THEN 
         var_tag:=‘i‘;
       ELSIF updating THEN
         var_tag:=‘u‘;
       ELSIF deleting THEN
         var_tag:=‘d‘;
       END IF;
       INSERT INTO dept_log 
       VALUES(var_tag,SYSDATE);
END tri_dept;

 

Step three:Launch a table operator in the trigger set.

INSERT INTO dept VALUES(9,‘a‘,‘a‘);

 

Step four:select dept_log table information

select * from dept_log;