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Query processing strategy

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Why is it not desirable to force users to make an explicit choice of a query processing strategy? Are there cases where it is desirable for users to be aware of the costs of competing query-processing strategies? Please explain.

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The expert examines query processing strategies.

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Dear Student,

The basic ingredients of the query decomposition are

(1) To discover pieces of a query which are joined to the remainder by a single joining variable

(2) To substitute for a variable. The overall strategy is to break up a query at the joining variables whereever possible, and to select a variable for substitution, which incurs a "cost" wherever substitution can no longer be ignored.

For simple queries, elaborate optimization may well do more harm ...

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  • MEngSc, University of Melbourne
  • Certificate IV in Training & Assessment , Australian Business Council
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