Question

I have 2 unrelated tables A and B which both have foreign key constraints on C. I need to run an sql query that determines if either A or B contain a given id of C. My first approach was to use the union all but A and B are not related thus it will not work.

Any ideas?

Answer 1

Not 100% sure what you’re asking but if you mean to return the elements of A and B that match the id in C then this will do it.

Select c.*, a.*, b.*
From c.id
    Left Outer Join a On a.id  = c.id
    Left Outer Join b On b.id = c.id
Where c.id = @somevalue and (a.id Is Not Null or b.id Is Not Null)

Where @somevalue is the value you’re looking for.