Ordering
Eliminating duplicate results
9. Select distinctive values in certain columns
Aggregation
Grouping
HAVING: filtering and ordering groups
Let's practice

Instruction

Excellent. You can also use DISTINCT on a group of columns. Take a look:

SELECT DISTINCT 
  customer_id, 
  order_date 
FROM orders;

One customer may place many orders every day, but if we just want to know on what days each customers actually did place at least one order, the above query will check that.

Exercise

Check what positions there are in every department. In order to do that, select the columns department and position from the table employees and eliminate duplicates.

Stuck? Here's a hint!

Type:

SELECT DISTINCT
  department, 
  position 
FROM employees;