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Database 1
Data Manipulation
Beer question n (tupel calculus)
This answer is wrong:
Suppose there are 2 beers a, b, 1 bar k, 2 drinkers x, y;
everyone serves/visits/likes everything
Then the correct answer should result in {a, b}.
The tupel calculus expression:
does not contain a, because every visitor of k also likes b.
The answer should have been:
Common tupel calculus mistakes
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