My quick answers for Jitbit's SQL interview questions. http://www.jitbit.com/news/181-jitbits-sql-interview-questions/ Discussion here: https://news.ycombinator.com/item?id=5779406 Sample data here: https://gist.github.com/abkr/5662615

gistfile1.sql

1. List employees (names) who have a bigger salary than their boss

  	SELECT
	e.`name`
	FROM
	employees AS e
	INNER JOIN employees AS b ON e.bossid = b.employeeid
	WHERE
	e.salary > b.salary

2. List employees who have the biggest salary in their departments

	SELECT
	emain.`name`,
	emain.salary
	FROM
	employees AS emain
	WHERE
		emain.employeeid = (
			SELECT
			esub.employeeid
			FROM
			employees AS esub
			WHERE
			esub.departmentid = emain.departmentid
			ORDER BY
			esub.salary DESC
			LIMIT 0, 1
		)
	GROUP BY
	emain.departmentid

3. List departments that have less than 3 people in it

	SELECT
	departments.`name`
	FROM
	departments
	LEFT JOIN employees ON employees.departmentid = departments.departmentid
	GROUP BY
	departments.departmentid
	HAVING
	COUNT(*) < 3

4. List all departments along with the number of people there (tricky - people often do an "inner join" leaving out empty departments)

	SELECT
	departments.`name`,
	Count(employees.employeeid) as count
	FROM
	departments
	LEFT JOIN employees ON employees.departmentid = departments.departmentid
	GROUP BY
	departments.departmentid

5. List employees that don't have a boss in the same department

	SELECT
	e.`name`
	FROM
	employees AS e
	INNER JOIN employees AS b ON e.bossid = b.employeeid
	WHERE
	e.departmentid <> b.departmentid

6. List all departments along with the total salary there

	SELECT
	departments.`name`,
	Sum(employees.salary)
	FROM
	departments
	LEFT JOIN employees ON employees.departmentid = departments.departmentid
	GROUP BY
	departments.`name`

Thanks for pointing that out @miguelangelnieto. I don't think I've ever come across that before (or I've just never noticed before!).

In fact I think we were both wrong. See https://news.ycombinator.com/item?id=5779842 for more info.

I've updated answer 2 now.