Q27

MCQMarks unknown

A library relational database system uses the following schema USERS (User#, User Name, Home Town) BOOKS (Book#, Book Title, Author Name) ISSUED (Book#, User#, Date) Explain in one English sentence, what each of the following relational algebra queries is designed to determine

(A)

$\sigma_{ \text{User#}=6}\left(\pi_{\text{User#, Book Title}}\left(\left(\text{USERS} \bowtie \text{ISSUED}\right) \bowtie \text{BOOKS}\right)\right)$

(B)

$\pi_{\text{Author Name}}\left(\text{BOOKS} \bowtie \sigma_{\text{Home Town=Delhi}} \left(\text{USERS} \bowtie \text{ISSUED}\right)\right)$

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