Ordering
Limiting the output
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 CustomerId, OrderDate FROM Order;
One customer may place many orders every day. However, we just want to know on what days each customer placed at least one order. The above query will check that.
Exercise
Check what positions there are in every department. To do so, select the Department and Position columns from the Employee table and eliminate duplicates.
Stuck? Here's a hint!
Type:
SELECT DISTINCT Department, Position FROM Employee;
