帮帮忙，看看这个sql的单表查询，该怎么解决比较好！

Question

表里现在是这样的id userid cid1 zhangsan 02 lisi 13 xiaowang 14 lizai 2查询的结果是id userid cid1 zhangsan 02 lisi zhangsan3 xiaowang zhangsan4 lizai lisi各位大神这个sql查询是怎么写啊

Answer 1

select id,userid,isnull((select userid from tb where id=t.cid),'0') as cid from tb as t