A bitmap index on the attribute A of relation r consists of one bitmap for each value that A can take. Each bitmap contains as many bits as the number of records in the relation.

The logical OR operation is used for the computation of the union of bitmaps. This is similar to the binary set union operation.

The complement operation in bitmaps is done by using the logical not operator. This is similar to the binary complement operation.

We create an index in SQL using the create index command. Eg: create index dept_index on instructor(dept_name).

A bitmap is simply an array of bits. A bitmap can be used for various purposes such as bitmap indexing.

An existence bitmap is used to recognize deleted records and not to prevent deletion of records. It also does not insert any records into empty bitmaps.

We delete and index in SQL using the drop index command. Syntax: drop index ;

Intersection operations are extremely fast on bitmaps making them ideal for supporting queries on multiple attributes.

The intersection of the bitmaps is done by the logical AND operation. This is similar to the binary set intersection operation which is done by the logical AND operation.

Bitmaps can be combined with B+ trees for relations where a few attribute values are extremely common.