Consider this query: Retrieve the Ssns of employees who work on at least those projects on which
Question:
Consider this query: Retrieve the Ssns of employees who work on at least those projects on which the employee with Ssn=123456789 works. This may be stated as (FORALL x) (IF P THEN Q), where
■ x is a tuple variable that ranges over the PROJECT relation.
■ P ≡ employee with Ssn=123456789 works on project x.
■ Q ≡ employee e works on project x.
Express the query in tuple relational calculus, using the rules
■ (∀ x)(P(x)) ≡ NOT(∃x)(NOT(P(x))).
■ (IF P THEN Q) ≡ (NOT(P) OR Q).
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Step by Step Answer:
Using the provided rules we can express the query in tuple relational calculus as follows eSsn e EMP...View the full answer
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Related Book For 
Fundamentals Of Database Systems
ISBN: 9780133970777
7th Edition
Authors: Ramez Elmasri, Shamkant Navathe
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