cityid与postcode对应，我想把postcode为空的都补上，postcode为空的对应的值在这个表里都有，请问为空的怎么补上
------解决思路----------------------
update tb set postcode=b.postcode from table1 tb left join (select distinct cityid,postcode from table1 where postcode<>'') b on tb.cityid=b.cityid
where tb.postcode=''
试试这个
------解决思路----------------------
with t as (
select distinct cityid,postcode
from 原表名
where isnull(postcode,'')<>''
)
update 原表名 set postcode=t.postcode
from 原表名 join t on t.cityid=原表名.cityid
where isnull(原表名.postcode,'')=''