Examples - Teradata Database

These examples show simple uses of the GROUP BY clause.

Also see “ROLLUP Grouping Set Option”, “CUBE Grouping Set Option”, and “GROUPING SETS Option”.

Example: Simple GROUP BY Operation

Generate a report of salary totals by department, the result might look something like the report that follows.

     SELECT dept_no, SUM(salary)
     FROM employee
     GROUP BY dept_no;

The result might be similar to the report that follows.

Example: Specifying a GROUP BY Clause on Nonaggregate Expressions When the Select List Includes an Aggregate

If you specify an aggregate in the select expression list of a query, then you must also specify a GROUP BY clause that includes all nonaggregate expressions from the select list. Otherwise, the system returns the following message.

     Selected non-aggregate values must be part of the associated group.

The system returns error message 3504 whenever an aggregate query includes a nonaggregate expression in its SELECT list, WHERE clause, ORDER BY clause, or HAVING clause, but not in a GROUP BY clause.

The system also returns this error when ORDER BY and WITH clauses specify aggregates, but the select list for the query does not.

For example, Teradata Database aborts the following query because it does not specify a GROUP BY clause that groups on the only nonaggregate expression in the select list, which is department_number:

     SELECT department_number, SUM(salary_amount)
     FROM employee
     WHERE department_number IN (100, 200, 300);

To work as intended, the query must be rewritten with an appropriate GROUP BY clause:

     SELECT department_number, SUM(salary_amount)
     FROM employee
     WHERE department_number IN (100, 200, 300)
     GROUP BY department_number;

The following statement aborts and returns an error because it does not specify all of the nonaggregate columns from the select list in its GROUP BY clause.

     SELECT employee.dept_no, department.dept_name, AVG(salary)
     FROM employee, department
     WHERE employee.dept_no = department.dept_no
     GROUP BY employee.dept_no;

In this case, the qualified nonaggregate column department.dept_name is missing from the GROUP BY clause.

The following statement aborts and returns an error because the nonaggregate grouping column specified in the ORDER BY clause is not also specified in the GROUP BY clause.

     SELECT employee.dept_no, AVG(salary)
     FROM employee, department
     WHERE employee.dept_no = department.dept_no
     ORDER BY department.dept_name
     GROUP BY employee.dept_no;

The following statement, based on the table definitions shown, aborts and returns an error because the aggregate query includes a nonaggregate expression, d1, in its HAVING clause, but not in the GROUP BY clause.

     CREATE TABLE t1(a1 int, b1 int, c1 int, d1 int);
     CREATE TABLE t2(a2 int, b2 int, c2 int, d2 int);
     SELECT min(a1) as i, max(b1) as j from t1
     GROUP BY c1
     HAVING 30 >= (sel count(*) from t2 where t1.d1=5);

The correct form of the query includes the nonaggregate expression, d1, in its HAVING clause and in the GROUP BY clause.

     SELECT min(a1) as i, max(b1) as j from t1
     GROUP BY c1, d1
     HAVING 30 >= (sel count(*) from t2 where t1.d1=5);

Example: Specifying GROUP BY Using an Ordered Analytic Function

The following statement specifies a GROUP BY clause with an ordered analytical function to generate report breaks where the function resets and computes a new value for the next grouping.

The example groups all items into percentile by profitability for each store and then returns only the items of interest, which, in this case, are the lowest percentile for each store.

     SELECT store, item, profit, QUANTILE(100, profit) AS percentile
     FROM (SELECT items.item, SUM(sales) -
                  (COUNT(sales)*items.item_cost) AS profit
           FROM daily_sales, items
           WHERE daily_sales.item = items.item
           GROUP BY items.item,items.itemcost) AS item_profit
     GROUP BY store, item, profit, percentile
     QUALIFY percentile = 99;

The result of this query looks like the following table:

store
-----

item
----

profit
------

percentile
----------

Eastside

Golf balls

    100.19

99

Westside

Tennis balls

   -110.00

99

Central

Bowling balls

   -986.81

99

South

Codfish balls

- 1,891.89

99

North

Bocce balls

  1,180.88

99

Example: SELECT Statement With a Scalar Subquery in Its GROUP BY Clause

The following example specifies a scalar subquery in its GROUP BY clause:

     SELECT sale_date, SUM(amount)
     FROM sales_table AS s
     GROUP BY sale_date, (SELECT prod_name 
                          FROM prod_table AS p
                          WHERE p.prod_no = s.prod_no);

Example: GROUP BY and PERIOD Value Expressions

The following example shows how the GROUP BY clause operates on PERIOD value expressions, where period_of_stay is the PERIOD value expression.

     SELECT emp_no, period_of_stay
     FROM employee
     GROUP BY emp_no, period_of_stay;