建立级联删除触发器CASCADE_DELETE,当删除部门时,级联删除EMP表的雇员记录。/*
CREATE TRIGGER CASCADE_DELETE
AFTER
DELETE OF deptno
ON DEPT
FOR EACH ROW
BEGIN
DELETE FROM EMP WHERE EMP.DEPTNO=:OLD.DEPTNO
END;
*/
delete from dept where deptno=50;
-- select * from emp;
--supdate emp set deptno=50 where empno=8888;
--select * from dept;
程序提示: delete from dept where deptno=50
*
第 1 行出现错误:
ORA-02292: 违反完整约束条件 (BOOKLQZ.FK_DEPTNO) - 已找到子记录
CREATE TRIGGER CASCADE_DELETE
AFTER
DELETE OF deptno
ON DEPT
FOR EACH ROW
BEGIN
DELETE FROM EMP WHERE EMP.DEPTNO=:OLD.DEPTNO
END;
*/
delete from dept where deptno=50;
-- select * from emp;
--supdate emp set deptno=50 where empno=8888;
--select * from dept;
程序提示: delete from dept where deptno=50
*
第 1 行出现错误:
ORA-02292: 违反完整约束条件 (BOOKLQZ.FK_DEPTNO) - 已找到子记录
after delete on dept
for each row
begin
delete emp where deptno=:old.deptno;
end;
SQL> select * from emp; EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- ------------------- ---------- ---------- ----------
7369 SMITH CLERK 7902 1980-12-17 00:00:00 800 900 20
7499 ALLEN SALESMAN 7698 1981-02-20 00:00:00 1600 300 30
7521 WARD SALESMAN 7698 1981-02-22 00:00:00 1250 500 30
7566 JONES MANAGER 7839 1981-04-02 00:00:00 2975 900 20
7654 MARTIN SALESMAN 7698 1981-09-28 00:00:00 1250 1400 30
7698 BLAKE MANAGER 7839 1981-05-01 00:00:00 2850 30
7782 CLARK MANAGER 7839 1981-06-09 00:00:00 2450 10
7788 SCOTT ANALYST 7566 1987-04-19 00:00:00 3000 900 20
7839 KING PRESIDENT 1981-11-17 00:00:00 5000 10
7844 TURNER SALESMAN 7698 1981-09-08 00:00:00 1500 0 30
7876 ADAMS CLERK 7788 1987-05-23 00:00:00 1100 900 20
7900 JAMES CLERK 7698 1981-12-03 00:00:00 950 30
7902 FORD ANALYST 7566 1981-12-03 00:00:00 3000 900 20
7934 MILLER CLERK 7782 1982-01-23 00:00:00 1300 10已选择14行。SQL> delete dept where deptno=30;已删除 1 行。SQL> select * from emp; EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- ------------------- ---------- ---------- ----------
7369 SMITH CLERK 7902 1980-12-17 00:00:00 800 900 20
7566 JONES MANAGER 7839 1981-04-02 00:00:00 2975 900 20
7782 CLARK MANAGER 7839 1981-06-09 00:00:00 2450 10
7788 SCOTT ANALYST 7566 1987-04-19 00:00:00 3000 900 20
7839 KING PRESIDENT 1981-11-17 00:00:00 5000 10
7876 ADAMS CLERK 7788 1987-05-23 00:00:00 1100 900 20
7902 FORD ANALYST 7566 1981-12-03 00:00:00 3000 900 20
7934 MILLER CLERK 7782 1982-01-23 00:00:00 1300 10已选择8行。
deptno是dept的主键,在emp中它是外键啊?
after delete on dept --删除都是整行 不需要指定列
delete from 和delete 是一样的
CREATE TRIGGER CASCADE_DELEDEPT
AFTER DELETE ON dept
FOR EACH ROW
BEGIN
DELETE FROM EMP WHERE EMP.DEPTNO=:OLD.DEPTNO
END;
*/
show error
--drop trigger cascade_delEdept;
LINE/COL ERROR
-------- -----------------------------------------------------------------
2/1 PL/SQL: SQL Statement ignored
3/3 PL/SQL: ORA-00933: SQL 命令未正确结束
7/0 PLS-00103: 出现符号 "end-of-file"在需要下列之一时:
begin case declare
end exception exit for goto if loop mod null pragma raise
return select update while with <an identifier>
<a double-quoted delimited-identifier> <a bind variable> <<
close current delete fetch lock insert open rollback
savepoint set sql execute commit forall merge pipe
少了分号
--为什么不用外键的记录删除的特性CREATE TRIGGER CASCADE_DELEDEPT AFTER DELETE ON dept FOR EACH ROW
BEGIN
DELETE FROM EMP WHERE EMP.DEPTNO=:OLD.DEPTNO;--分号
END;
2楼的方法相当于平时我们所使用的级联删除方法???