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Applying the Algebraic laws for query optimization

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• Sample query optimization using algebraic laws
  • Query:

    For each (movie) year, find the earliest birthday (youngest movie star) in that (movie) year

    SQL command:

    SELECT movieYear. max( birthday ) FROM movieStar, StarsIn WHERE name = starName GROUP BY movieYear

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  • The initial logical query plan is as follows:

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  • Apply:

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  • Apply:

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  • Optionally, you can insert a harmless projection at the top:

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  • Optionally, you can insert a couple of harmless projections at the bottom: