Question

How do I filter my Linq-to-SQL query so that it only shows records that aren’t referenced (via a FK) in another table?

So for example, I had two tables: TableA and TableB. TableB had a FK referencing TableA. I want to select all rows from TableA that have no records in TableB referencing it.

In raw T-SQL, I can do:

SELECT * FROM TableA
WHERE NOT EXISTS (SELECT * FROM TableB WHERE TableA._id = TableB.fk_tablea_id)

In raw MySQL, I can do a left join and use the ISNULL() function in the where clause.

I’m not sure of the best way to do this with LINQ to SQL.

Answer 1

You can do the below:

var ctx = new Context();
var rowAs = from TableA in ctx.TableAs
             where TableA.TableB.Count() > 0
             select TableA;