create table emp(EMPNO varchar2(20),ENAME varchar2(20),deptno varchar2(20),dname varchar2(20));
insert into emp values(7599,'WORD',30,'CCC');
select * from emp;
EMPNO ENAME DEPTNO DNAME
1 7369 SMITH 20 AAA
2 7499 ALLEN 10 BBB
3 7599 WORD 30 CCC
create table dept (deptno varchar2(20),dname varchar2(20));
insert into dept values(10,'SALES');
insert into dept values(20,'IT');
insert into dept values(30,'HR');
UPDATE emp
SET emp.dname =
(SELECT dept.dname
FROM dept
WHERE dept.deptno = emp.deptno
AND dept.deptno IN (10, 20));
select * from emp;
EMPNO ENAME DEPTNO DNAME
1 7369 SMITH 20 IT
2 7499 ALLEN 10 SALES
3 7599 WORD 30
可以看到deptno=30的被更新成空的了
select * fr
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