Question

I have 3 tables, Client, Tool and ClientTools.
One client can have multiple tools, so ClientTools acts as pivot table (only containing Id’s).

What I would like to do is, for a given Client, to have a full list of tools, and a flag indicating whether the Client has this tool or not.

Where I came so far is :

select      t.Id as [ToolId],
            t.Name as [ToolName],
            Cast(case when c.Id is NULL then 0 else 1 end as bit) as [HasThisTool],
from        Tool t
Left join   ClientTools ct
on          t.Id = ct.ToolId
Left Join   Client c
on          ct.ClientId = c.Id

Which correctly gives me all Tools, but for all Clients (duplicating Tool rows when multiple clients own this Tool).

But as soon as I use a where close to filter to the selected client, my query only returns the rows for this client (so the left join is not made anymore).

I tried adding where c.Id = 123
and
where (c.Id = 123 or c.Id is null) but none worked.

What am I missing ?

Thanks in advance !

Answer 1

Try:

select      t.Id as [ToolId],
            t.Name as [ToolName],
            Cast(case when ct.Id is NULL then 0 else 1 end as bit) as [HasThisTool]
from        Tool t
Left join   ClientTools ct
on          t.Id = ct.ToolId and ct.ClientId = @ClientId