Set rules

Learn column count and type rules for set queries.

Set operation rules

In set operations each SELECT must have the same column count and compatible types. Ordering is only on the last query.

SELECT name, city FROM customers
UNION
SELECT name, city FROM suppliers
ORDER BY name;

This query sorts the combined list by name.

name, city is selected from customers. The result is sorted by name in ascending order.

ORDER BY is written only after the last SELECT. It cannot appear in intermediate queries.

That ORDER BY sorts the whole combined result; you refer to columns by their names in the first SELECT or by position.

Combine customers and suppliers with UNION and sort with ORDER BY name.

Show example solution

SELECT name, city FROM customers
UNION
SELECT name, city FROM suppliers
ORDER BY name;

Add ORDER BY

SELECT name, city FROM customers
UNION
SELECT name, city FROM suppliers
____ name;

Show answer

SELECT name, city FROM customers
UNION
SELECT name, city FROM suppliers
ORDER BY name;