Question

我有一个名为Team_table的表，其中Team_Id列为主键，4个不同的表为Team_Member，Team_Project，Team_Account， Team_link也包含此Team_Id。

在从Team_table删除团队之前，我必须在所有4个表中检查其引用。如果在任何一个表中找到此Team_Id，则用户无法将其删除。

我做了以下查询但是没有工作 -

select count(Team.Team_Id)
  from Team 
  join Team_Project on Team.Team_Id = Team_Project.Team_Id  
 right join Team_Member on Team.Team_Id = Team_member.Team_Id  
 right join Team_link on Team.Team_Id = Team_link.Team_Id  
 right join Team_Account on Team.Team_Id = Team_Account.Team_Id  
 where Team.Team_Id = 2

但它总是给我0，而这个team_Id在所有表格中都可用请建议我正确的解决方案

Answer 1

试试这个：

declare @teamid int=2;

Select Team_Id from Team_Project where Team_Id=@teamid union all
Select Team_Id from Team_Member  where Team_Id=@teamid union all
Select Team_Id from Team_link    where Team_Id=@teamid union all
Select Team_Id from Team_Account where Team_Id=@teamid; 

if @@ROW_COUNT=0 delete from TEAM where Team_Id=@teamid

Answer 2

一组right join结束为空，最后一个表为空。如果第一个表为空，则一组left join结束为空。但是一组full join将返回任何匹配的行。因此，请考虑将right join替换为full join。

作为另一种选择，我发现使用not exists子句代替join进行此类查询更清晰：

delete  t
from    Team t
where   t.Team_Id = @TeamId
        and not exists (select * from Team_Project where Team_Id = @TeamId)
        and not exists (select * from Team_Member where Team_Id = @TeamId)
        and not exists (select * from Team_link where Team_Id = @TeamId)
        and not exists (select * from Team_Account where Team_Id = @TeamId)

根据您的评论，检索计数：

select  count(*)
from    (
        select  Team_Id 
        from    Team_Project 
        union all
        select  Team_Id 
        from    Team_Member  
        union all
        select  Team_Id 
        from    Team_link    
        union all
        select  Team_Id 
        from    Team_Account 
        ) as SubQueryAlias
where   Team_Id = @TeamId

Answer 3

select count(Team.Team_Id) 
from Team 
left join Team_Project 
   on Team.Team_Id=Team_Project.Team_Id  
left join Team_Member 
   on Team.Team_Id=Team_member.Team_Id  
left join Team_link 
   on Team.Team_Id=Team_link.Team_Id  
left join Team_Account 
   on Team.Team_Id= Team_Account.Team_Id  
where Team.Team_Id=2 and 
(Team_Project.Team_Id is not null
 of 
 Team_member.Team_Id is not null
 or 
 Team_link.Team_Id is not null
 or
 Team_Account.Team_Id is not null)

在删除该列值之前，我需要一个SQL查询来检查4个不同表中可用列值的引用

3 个答案: