Question

要求：一条SQL语句先判断表2与表1的sale值不一致的数据，然后按照table1的值update掉table2的值。

Answer 1

update table2 set table2.sale=table1.sale
from table2,table1 where table2.date=table1.date andtable2.ID=table1.ID and table2.sale<>table1.sale

Answer 2

update table2 set sale =
(
select sale from table1
where table1.date = table2.date and table1.id = table2.id
)
where exists
(
select * from table1
where table1.date = table2.date and table1.id = table2.id
)
--效果有点出入，但是是一样的