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SQL Basics in PostgreSQL

Ordering
Limiting the output
Eliminating duplicate results
Aggregation
14. Count distinctive values in a column
Grouping
HAVING: filtering and ordering groups
Let's practice

Instruction

Great. As you probably expect, we can also add the DISTINCT keyword in our COUNT() function:

SELECT COUNT(DISTINCT customer_id) AS distinct_customers
FROM orders;

This time, we count all rows which have a distinctive value in the column customer_id. In other words, this instruction tells us how many different customers have placed an order so far. If a customer places 5 orders, the customer will only be counted once.

Exercise

Count how many different positions there are in the employees table. Name the column distinct_positions.

Stuck? Here's a hint!

Type:

SELECT COUNT(DISTINCT position) AS distinct_positions
FROM employees;