Question

SQL如何将两张表进行对比更新

现有两个表,一个表为T1表,另一个为T2表,
T1表和T2表有共同字段K1, T1表的A,B字段值不正确,需要读取T2表的A,B字段值来更新,
要达到的目的是,如果T1表中的K1字段与T2表的K1字段相同,刚T1表的A,B值应等于T2表AB值,否则,其值保持原有不变.

Answer 1

update t1 set (t1.a,t1.b)=(select t2.a,t2.b from t2 where t1.k1=t2.k1)

Answer 2

update T1 SET A=T2.A,B=T2.B
FROM T1,T2
WHERE T1.K1=T2.K1

Answer 3

update T1 SET A=T2.A,B=T2.B FROM T2 WHERE T1.K1=T2.K1