Question

I have a table named as Team_table having a column Team_Id as a primary key, and 4 different table are Team_Member, Team_Project, Team_Account, Team_link also contains this Team_Id.

Before deleting a team from Team_table, I have to check its reference in all 4 tables. if this Team_Id found in any one table, user cant delete it.

I made following query but its not working-

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

But its always giving me 0, while this team_Id is available in all tables.
Please suggest me right solution

Answer 1

A group of right join ends up empty the last table is empty. A group of left join ends up empty if the first table is empty. But a group of full join will return any matching rows. So consider replacing your right join with full join.

As another option, I find it clearer to use not exists clauses instead of join for this kind of query:

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)

Per your comment, to retrieve the count:

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