About Indexes

Indexes are supportive objects for tables which can improve the speed of random selection queries against a table. While there are several types of indexes supported within an Oracle database, the most common is a B-tree index which stores the index column values and associated RowIDs. We will consider B-tree indexes within this section.

Which B-tree Indexes Might Exist?

These different B-tree indexes are typical of what might be found in a heavily accessed table:

• When a primary key constraint is defined on the primary key column, the database will implicitly and automatically create a B-tree index to enforce the constraint. However, this index will also be available for any operation which references the primary key column. The MemberID column serves as the primary key.