sql语句中左连接,case when 替换语句的并用,替换结果答:可以用isnull函数:select a.*,isnull(b.id,0) as [id],isnull(b.job,0) as [job],isnull(b.parent_id,0) as [parent_id]from a left join b on a.id=b.parent_id 或者用case when 语句 select a.*,case b.id when null then 0 else b.id end as [id],case b...