What will be the correct output of this query

Question

Consider the following relational schema
Suppliers(sid:integer, sname:string, city:string, street:string)
Parts(pid:integer, pname:string, color:string)
Catalog(sid:integer, pid:integer, cost:real)

Consider the following relation query for the above database

Select S.sname
From Suppliers S
Where S.sid NOT in (select C.sid from Catalog C where C.pid not in (Select p.pid from Parts P where P.color<>'blue'))

Is it correct query for getting the name of supplier who have supplied a non blue part or it is returning something else

Answer 1

Preity Considering it's nearly 3am EDT, I may not be thinking most clearly... But your query seems to make sense and at first glance should work.

Have you attempted using outer joins and filtering on null matches instead?

That's the approach I would have gone.