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The process of replacing a nested query with a query with a join is known as _________(a) Correlation(b) Decorrelation(c) Cache handling(d) Join replacementI had been asked this question in exam.This is a very interesting question from Choice of Evaluation Plans topic in section Query Processing and Optimization of RDBMS

Answer»

Right answer is (b) Decorrelation

Easiest explanation: The PROCESS of replacing a nested query with a query with a join is KNOWN as decorrelation. It is more COMPLICATED when the nested sub query uses aggregate functions INSIDE it.



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