Confirmation of Oracle Database Trigger Data

a need

Wages cannot be raised more or less.

 

two code

1. --触发器应用场景2：数据的
2. --涨后的薪水不能少于涨前的薪水
3. /*
4. :old和：new代表的是同一条记录
5. :new 表示操作该行之前，这一行的值
6. :old 表示操作该行之后，这一行的值
7. */
9. create or replace trigger checksalary
10. before update
11. on emp
12. for each row
13. begin
14. if:old.sal >:new.sal then
15. raise_application_error(-20002,'涨后的薪水不能少于涨前的薪水 涨前'||:old.sal||'涨后'||:new.sal);
16. endif;
17. end;
18. /

 

Three verification

SQL> update emp set sal=sal+1 where empno=7839;

 

1 row updated.

 

SQL> update emp set sal=sal-1 where empno=7839;

update emp set sal=sal-1 where empno=7839

       *

Error on line 1:

ORA-20002: The salary after the increase cannot be less than the salary before the increase 10101 before the increase 10100 after the increase

ORA-06512: 在 "SCOTT.CHECKSALARY", line 3

ORA-04088: error during execution of trigger 'SCOTT.CHECKSALARY'