DB2 can implement a join in three ways using a m

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DB2 can implement a join in three ways using a merge join...

Q: DB2 can implement a join in three ways using a merge join, a nested join or a hybrid join. Explain the differences?

AN:
A merge join requires that the tables being joined be in a sequence; the rows are retrieved with a high cluster ratio index or are sorted by DB2. A nested join does not require a sequence and workd best on joining a small number of rows. DB2 reads the outer table values and each time scans the inner table for matches, The hybrid join is a nested join that requires the outer table be in sequence.

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