Designing queries to retrieve only required data

To ensure that your query retrieves only the required data:

• Ensure that you have used appropriate predicates.

  For example, check to see that the selectivity value for the predicates is as small as possible.

  If cardinality on the Operator Details window equals zero, check to ensure that you used therunstats command after making your table updates.

• Qualify your SELECT statements so that they retrieve only those columns that provide the data you need.

For more information about using SELECT statements and choosing predicates, see the section on tuning queries in the Administration Guide.