What is Join index

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Answered by: rin23

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Member Since May-2011 | Answered On : May 12th, 2011

A join Index is a cross between a view and an index. It is like a view in that it is created using a query to specify the structure, composition and source of the contents. It is like an index in the way that it is used automatically by the database system to improve the performance of a query. Join indexes use the "classic" space-time trade off trading disk space for storage of the join index to get improved performance for queries. Unlike many other materialized view implementations, Teradata join indexes are updated immediately and automatically when changes are made to the base tables. There is never a concern that you might be using stale data when the system chooses to use a join index in the query plan. Also, Teradata uses its sophisticated coverage testing algorithm to minimize the cost associated with join index maintenance.