ASA SQL User's Guide
Query Optimization and Execution
Indexes can greatly improve the performance of searches on the indexed column(s). However, indexes take up space within the database and slow down insert, update, and delete operations. This section will help you to determine when you should create an index and tell you how to achieve maximum performance from your index.
There are many situations in which creating an index improves the performance of a database. An index provides an ordering of the rows of a table on the basis of the values in some or all of the columns. An index allows Adaptive Server Anywhere to find rows quickly. It permits greater concurrency by limiting the number of database pages accessed. An index also affords Adaptive Server Anywhere a convenient means of enforcing a uniqueness constraint on the rows in a table.
The Index Consultant is a tool that assists you in the selection of an appropriate set of indexes for your database. For more information, see Index Consultant overview.
When to create an index
Improving index performance
Other uses for indexes
Types of index