View implementation

 

Views, derived tables (nested table expressions or NTEs), and common table expressions (CTEs) are implemented by the query optimizer using one of two methods.

These methods are:

• The optimizer combines the query select statement with the select statement of the view.

• The optimizer places the results of the view in a temporary table and then replaces the view reference in the query with the temporary table.

• View composite implementation
  The view composite implementation takes the query select statement and combines it with the select statement of the view to generate a new query. The new, combined select statement query is then run directly against the underlying base tables.

• View materialization implementation
  The view materialization implementation runs the query of the view and places the results in a temporary result. The view reference in the user's query is then replaced with the temporary, and the query is run against the temporary result.

 

Parent topic:

Processing queries: Overview