Oracle SQL Performance Tuning Tips-Using Indexes to Improve Performance a to z help

Oracle SQL Performance Tuning Tips-Using Indexes to Improve Performance a to z help

•Indexes primarily exist to enhance performance. But they do not come without a cost.  Indexes must be updated during INSERT, UPDATE and DELETE operation, which may slow down performance

 

•Besides, the usefulness of an Index depends on selectivity of a column/columns.

 

•Generally Indexes are more selective if the column/columns have a large number of unique values.

 

•If an Index contains more than one column, it is called CONCATENATED INDEX .

 

•Concatenated index is often more selective than a single key index.

 

•Column positions play an important role in Concatenated index.  While using Concatenated Index, be sure to use LEADING columns

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