projection

Consider a relational database schema with two relations $R(P, Q)$ and $S(X, Y)$. Let $E=\{\langle u\rangle \mid \exists v \exists w\langle u, v\rangle \in R \wedge\langle v, w\ran...

SELECT operation in SQL is equivalent to

A library relational database system uses the following schema USERS (User #, User Name, Home Town) BOOKS (Books # Book Title, Author Name) ISSUED (Book #, User #, Date) Explain in...