SQL Functions and Statements
WITHIN GROUP ORDER BY Clause for Aggregate Functions
Several Vertica functions now support the WITHIN GROUP ORDER BY clause, which lets you sort within each group of aggregated values. For example, the following query calls ARGMAX_AGG in a WITH clause to find which employees in each region are at or near retirement age. If multiple employees within each region have the same age, ARGMAX_AGG uses the WITHIN GROUP ORDER BY clause to choose employees with the highest salary level, and returns with their IDs. The primary query returns with details on the employees selected from each region:
=> WITH r AS (SELECT employee_region, ARGMAX_AGG(employee_age, employee_key) WITHIN GROUP (ORDER BY annual_salary DESC) emp_id FROM employee_dim GROUP BY employee_region ORDER BY employee_region) SELECT r.employee_region, ed.annual_salary AS highest_salary, employee_key, ed.employee_first_name||' '||ed.employee_last_name AS employee_name, ed.employee_age FROM r JOIN employee_dim ed ON r.emp_id = ed.employee_key ORDER BY ed.employee_region; employee_region | highest_salary | employee_key | employee_name | employee_age ----------------------------------+----------------+--------------+------------------+-------------- East | 927335 | 70 | Sally Gauthier | 65 MidWest | 177716 | 869 | Rebecca McCabe | 65 NorthWest | 100300 | 7597 | Kim Jefferson | 65 South | 196454 | 275 | Alexandra Harris | 65 SouthWest | 198669 | 1043 | Seth Stein | 65 West | 197203 | 681 | Seth Jones | 65 (6 rows)
You can use WITHIN GROUP ORDER BY clauses with the following functions:
This clause is also supported for user-defined aggregate functions.