Question

I’m using mssql

How do I do a outer join on three tables, one of which is a junction table?

There can be nulls in the menu or product tables and I need these included in the result.

SELECT *
from [web].[dbo].[tblMenus]
left outer JOIN [web].[dbo].[tblProductsRelMenus] 
on [tblMenus].Id  = [tblProductsRelMenus].MenuId
left outer JOIN [web].[dbo].[tblProducts] 
on [tblProductsRelMenus].ProductId = [tblProducts].ProductId

This doesn’t give menu nulls, and if I change the second left to a right, I loose the product nulls…

What is the correct way to do this?

Answer 1

Perhaps you are looking for a full outer join

SELECT *
from [web].[dbo].[tblMenus]
full outer JOIN [web].[dbo].[tblProductsRelMenus] 
on [tblMenus].Id  = [tblProductsRelMenus].MenuId
full outer JOIN [web].[dbo].[tblProducts] 
on [tblProductsRelMenus].ProductId = [tblProducts].ProductId