Expert Indexing in Oracle Database 11g: Maximum Performance for Your Database

Managing B-tree Indexes with Constraints

B-tree indexes and primary key and unique key constraints are inseparable. This is because Oracle uses these indexes to enforce primary key and unique key constraints. You can't have an enabled primary key or unique key constraint without an associated B-tree index.

When you create a primary key or unique key constraint, you have the option of having Oracle automatically create the corresponding index. In this scenario, if you drop or disable the constraint, Oracle will also automatically drop the corresponding index.

You can also create the index separately from the constraint. When you create the index and constraint separately, this allows you to drop or disable the constraint without automatically ...