UPDATE STUDENT S
SET GRADE=(select G.GRADE FROM GRADE G WHERE S.ID=G.ID)
where exists(select G.GRADE FROM GRADE G WHERE S.ID=G.ID);
SET GRADE=(select G.GRADE FROM GRADE G WHERE S.ID=G.ID)
where exists(select G.GRADE FROM GRADE G WHERE S.ID=G.ID);
谢谢,看明白了,而且很好理解。where子句中找出要更新的行,set子句对这一行进行更新。good!!
结帖。