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Categories / Oracle PLSQL Tutorial / Analytical Functions

 

The Order in Which the Analytical Function Is Processed in the SQL Statement

SELECT FROM x WHERE is executed by the database engine by scanning a table, x, and retrieving rows when the WHERE clause is true. WHERE is often called a "row filter." The SELECT .. FROM .. WHERE may contain joins and GROUP BY as well as WHERE. If there were GROUPING and HAVING clauses, then the criteria in HAVING would be applied after the result of the SELECT .. WHERE is completed. HAVING is often called an "after filter". HAVING is after the WHERE, and after the GROUP BY is executed. The ordering is done last, after the result set has been established from SELECT .. FROM .. WHERE .. HAVING. The analytical function is performed just before the ORDER BY. All grouping, joins, WHERE clauses, and HAVING clauses will have already been applied.