Qualifying data

Qualification by the database server

Qualification by the access method
An access method might perform all the qualification tests or it might examine some of the values that a WHERE clause specifies to partially qualify rows.

Qualification by external software
If required, an access method can pass a qualification to external software. To exchange information with external software, the access method must manage communication.

Support for query plan evaluation
At the start of a SELECT statement, the database server initiates query planning. A query plan specifies the steps that the database server takes to fulfill a query with optimal efficiency.