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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

  1.  $\sigma_{ \text{User#}=6}\left(\pi_{\text{User#, Book Title}}\left(\left(\text{USERS} \bowtie \text{ISSUED}\right) \bowtie \text{BOOKS}\right)\right)$
  2.  $\pi_{\text{Author Name}}\left(\text{BOOKS} \bowtie \sigma_{\text{Home Town=Delhi}} \left(\text{USERS} \bowtie \text{ISSUED}\right)\right)$
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  1. Select the (user# and) titles of the books issued to User# 6
  2. Select author names of the books issued to users whose home town is Delhi
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(a) select all the book title which are issued by user id =6

 

(b) select all the author name whose book are issued by user belongs to home town delhi

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