Sorting by Several Columns

ORDER BY can take more than one column. SQL sorts by the first one, then uses the next to break ties.

Everyone grouped by department, highest paid first inside each one:

SELECT first_name, department_id, salary
FROM employees
ORDER BY department_id, salary DESC;

Each column gets its own direction. Here department_id sorts ascending (the default) and salary sorts descending.

Ties matter more than you'd think. Three engineers were hired on 2020-03-15, so their order here isn't guaranteed:

SELECT first_name, hire_date FROM employees
ORDER BY hire_date;

Add a second column and the order becomes predictable:

SELECT first_name, hire_date FROM employees
ORDER BY hire_date, first_name;

You can also sort by an alias from SELECT:

SELECT first_name, ROUND(salary / 12.0) AS monthly
FROM employees
ORDER BY monthly DESC;