A number in the ORDER BY

Question

In the ORDER BY clause, what impact does '5' have on the whole query output? I thought ORDER BY could only work in relations with DESC or ASC.

SELECT
employee_id,
first_name,
last_name,
hire_date,
salary
FROM
employees
WHERE
(salary * 1.5) < 15000
ORDER BY
hire_date, 5;

Answer 1

A number 'n' in the ORDER BY clause refers to the nth field in your SELECT clause.

In your example, number 5 refers to the salary column in the SELECT. It will therefore order by hire_date first, then on salary second.