Time Costs of a Query

This section explains the response-time effects of actions that the database server performs as it processes a query.

Many of the costs described cannot be reduced by adjusting the construction of the query. A few can be, however. The following costs can be reduced by optimal query construction and appropriate indexes:

• Sort time
• Data mismatches
• In-place ALTER TABLE
• Index lookups

For information about how to optimize specific queries, see Improving Individual Query Performance.