Should I index primary key column(s) in Oracle

Question

I\'ve recently stopped to think that Primary Keys are not indexes, they\'re a combination of Unique and Null constraints. And till now, I\'ve never created index for PK colu

Answer 1

Oracle will create an index for you, or can use an existing one. Whether a unique or non-unique index is used is up to you.

http://docs.oracle.com/cd/B28359_01/server.111/b28310/indexes003.htm#i1006566

A primary key itself is not an index, and nor is a unique constraint -- they are both constraints. However an index is used to support them.

A unique index is rather different as it can exist in the absence of a unique or primary key constraint, and neither constraint type require that the index supporting it be unique.