Ordering
Eliminating duplicate results
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;
