Consider the following relational schema: Suppliers(sid:integer, sname:string,…

GATE · 2009 · CSModified — slightly modified from the official paper; see the solution

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 relational query on 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'))

Assume that relations corresponding to the above schema are not empty. Which one of the following is the correct interpretation of the above query?

A.
Find the names of all suppliers who have not supplied a blue part.
B.
Find the names of all suppliers who have not supplied a non-blue part.
C.
Find the names of all suppliers who have supplied only blue parts.
D.
Find the names of all suppliers who have not supplied only blue parts.

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