decide how to add indexes on the column

Hi all

I get about confious using index

When should I decide to add index?

http://docs.Oracle.com/CD/E11882_01/server.112/e25789/indexiot.htm#CNCPT811

In general, consider creating an index on a column in any of the following situations:

    The indexed columns are queried frequently and return a small percentage of the total number of rows in the table.

    A referential integrity constraint exists on the indexed column or columns. The index is a means to avoid a full table lock that would otherwise be required if you update the parent table primary key, merge into the parent table, or delete from the parent table.

    A unique key constraint will be placed on the table and you want to manually specify the index and all index options.

Tags: Database

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