Delete from join 用法

Posted 2020-10-11 代码艺术

delete (别名) from tblA (别名) left join tblb (别名) on。。。用法

 

1、创建使用的表及数据

CREATE TABLE YSHA 
(
    code VARCHAR(10),
    NAME VARCHAR(20)
)

CREATE TABLE YSHB
( 
   code VARCHAR(10),
   col VARCHAR(10)
)

INSERT INTO YSHA VALUES (1,‘A1‘)
INSERT INTO YSHA VALUES (2,‘A2‘)

INSERT INTO YSHB VALUES(1,‘Row1‘)
INSERT INTO YSHB VALUES(1,‘Row2‘)
INSERT INTO YSHB VALUES(1,‘Row3‘)
INSERT INTO YSHB VALUES(3,‘Row1‘)

2、delete from left join

DELETE A FROM YSHA A LEFT JOIN YSHB B ON A.code=b.code WHERE b.code is NULL
SELECT * FROM YSHA
SELECT * FROM YSHB

DELETE FROM YSHA WHERE NOT EXISTS(SELECT 1 FROM YSHB B WHERE YSHA.code=b.code )
SELECT * FROM YSHA
SELECT * FROM YSHB