Sams Teach Yourself SQL in 21 Days, Fourth Edition

Summary

Indexes are physical database objects stored by your database management system that can be used to retrieve data already sorted from the database. In addition, thanks to the way indexes are mapped out, using indexes and properly formed queries can yield significant performance improvements.

The basic syntax used to create an index looks like this:

CREATE INDEX index_name
ON table_name(field_name(s));