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Dbms

The document outlines a set of relational algebra queries based on a schema involving Suppliers, Parts, and Catalog relations. It includes tasks such as finding supplier names for red parts, supplier IDs for red or green parts, and comparisons of pricing between suppliers. The queries also explore conditions related to supplying every part or specific colors, as well as identifying parts supplied by multiple suppliers.

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11 views2 pages

Dbms

The document outlines a set of relational algebra queries based on a schema involving Suppliers, Parts, and Catalog relations. It includes tasks such as finding supplier names for red parts, supplier IDs for red or green parts, and comparisons of pricing between suppliers. The queries also explore conditions related to supplying every part or specific colors, as well as identifying parts supplied by multiple suppliers.

Uploaded by

alter.whayu
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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In-class Exercise Relational Algebra

Consider the following schema:

Suppliers(sid: integer, sname: string, address: string)


Parts(pid: integer, pname: string, color: string)
Catalog(sid: integer, pid: integer, cost: real)

The key fields are underlined, and the domain of each field is listed after the field
name. Therefore sid is the key for Suppliers, pid is the key for Parts, and sid and pid
together form the key for Catalog. The Catalog relation lists the prices charged for
parts by Suppliers. Write the following queries in relational algebra.

1. Find the names of suppliers who supply some red part.

2. Find the sids of suppliers who supply some red or green part.

3. Find the sids of suppliers who supply some red part or are at 221 Packer Street.

4. Find the sids of suppliers who supply some red part and some green part.

5. Find the sids of suppliers who supply every part.


6. Find the sids of suppliers who supply every red part.

7. Find the sids of suppliers who supply every red or green part.

8. Find the sids of suppliers who supply every red part or supply every green part.

9. Find pairs of sids such that the supplier with the first sid charges more for some part than
the supplier with the second sid.

10. Find the pids of parts supplied by at least two different suppliers.

11. Find the pids of the most expensive parts supplied by suppliers named Yosemite Sham.

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