15.10 - QUALIFY Clause - Teradata database with examples, how to use it, and usage
There is a clause in the SELECT statement that filters the results of a previously computed analytical function.
Similar to HAVING, an introduction to a conditional clause further filters rows from aWHERE clause.The main difference between the two is that with QUALIFY the filters are based on the result of performing various analytical functions.
QUALIFY allows you to specify analytical functions and subqueries as search conditions.
In a search condition, the value for a rowlevel security constraint must be expressed in its encoded form.
A null evaluates to unknown with a DEFAULT function compared to a condition other than IS.
There is more information about the DEFAULT function.
When the WHERE, GROUP BY, and QUALIFY clauses are used together in a SELECT statement, the order of evaluation is as follows:
There is a clause in the Where clause.
Group by clause.
There is aQUALIFY clause.
The FROM clause tables are evaluated by the Teradata Database.
Group BY columns are used to group the rows.
The ordered analytical functions on the table are evaluated by the database.