From the course: Oracle Database 19c: Advanced SQL

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Overview of indexes

Overview of indexes - Oracle Database Tutorial

From the course: Oracle Database 19c: Advanced SQL

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Overview of indexes

- [Instructor] Non-unique indexes unlike unique indexes are not used for integrity checking, but instead primarily for performance reasons. This lesson applies to indexes in general, but non-unique indexes in particular since they don't have a specific role for enforcing database constraints, like unique constraints, primary key constraints, and so forth. In all cases, an index can speed performance of a query if only a small number of rows is needed, and the search column is part of an index. For non-unique indexes, this is the only basic function, all of the unique index types can be used to enforce a constraint, and also maintain an index but make it hidden. This can facilitate database tuning if the index makes the query run longer. Also, I often compress my indexes, and you can use one of four compression levels on an index. Many times the slight extra overhead of compressing and decompressing an index is offset by a significant reduction in that all lapse time much like advanced…

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