oracle外键解说
oracle外键解说
以下为在plsql中所试验的语句,可以反映外键的使用方法及作用:
create table job (jid int primary key ,jname varchar2(10));
create table dept (depid int primary key ,depname varchar2(10));
create table emp
(
eid int primary key ,
ename varchar2(10),
jno int constraint fk_jid references job(jid) on delete cascade,
depno int constraint fk_pid references dept(depid)on delete set null)
select * from job
select * from dept
select * from emp
insert into job(jid,jname) values(1,'china')
insert into job(jid,jname) values(3,'japan')
insert into dept(depid,depname) values(2,'b')
insert into dept(depid,depname) values(3,'c')
insert into emp(eid,ename,jno,depno) values(8,'z',1,2)
delete from dept where depid=2
select * from emp
delete from job where jid=1
select * from emp