sql语句 根据条件update

sql语句 根据条件update

update B
set B.div = (case
when B.id in (select distinct id from A) then (select div from A where id = B.id)
else (select div from A where id='00') end
)
from A,B
where B.div is null

update b
set b.div = (case
when b.id in (select distinct div from a) then a.div
when b.id not in (select distinct div from a) then '00'
)
from a,b
where b.div is null追问感谢回答，你可能理解错了我的意思。
当B表的ID在A表里不存在时，是用A表里面ID为00的DIV更新，而不是用“00”来更新。
不过还是很感谢。

先运行
update B set div = a. a2
from
(
select ID as a1
,DIV as a2
from A
) as a
where div is null
and ID = a.a1

再运行
update B set div = a. a2
from
(
select ID as a1
,DIV as a2
from A
where ID = 00
) as a
where div is null追问感谢回答，第一段SQL语句是把ID相同的先更新掉，第二段是把ID不同的固定用00的DIV来更新。
能不能用一段SQL语句来做呢？追答2个语句可以放在一起运行的，先后顺序不要搞反

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