Process queries that involve a virtual index
This section describes various options for processing a SELECT statement, or query, that involves a virtual index.
An SQL query requests that the database server fetch and assemble stored data into rows. A SELECT statement often includes a WHERE clause that specifies the values that a row must have to qualify for selection.
Query processing involves the following actions:
- Interpreting the scan and qualification descriptors
- Scanning the index to select index entries
- Optionally returning rows that satisfy the query
- Maintaining cost and distribution information for the optimizer