Oracle，用left join 替代 exists ,not exists,in , not in，提高效率

Not IN问题

Exists，not Exists，in，not in

例如：

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

等同于

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