Q55

Consider the following relational schema: $\text{Suppliers}(\underline{\text{sid:integer}},\text{ sname:string, city:string, street:string})$ $\text{Parts}(\underline{\text{pid:integer}}, \text{ pname:string, color:string})$ $\text{Catalog}(\underline {\text{sid:integer, pid:integer}}, \text{cost:real})$ 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?