方法一：
update table1 set field1=table2.field1 from table2
where table1.id=table2.id
--简写
update t1 set t1.c2 = t2.c2 from t2
where t1.c1 = t2.c1
方法二：
update table1
set field1=(select top 1 field1 from table2 where table2.id=table1.id)
where table1.id in (condition)