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Jitbit's SQL interview questions

May 27 2013

Since we're selling a help desk ticketing system we have lots of IT people among our customers - programmers, IT-support agents, system administrators, database engineers... In other words - there must be a lot of engineers reading this blog. So we decided to share our SQL interview questions we give our candidates, you people might find it useful.

Even though most of our work is based around Microsoft SQL Server and the test machine we provide is connected to an MS SQL database, the test would fit any database engine - Oracle, PostgreSQL, MySQL - anything, since it's very basic.

Some people might say it is too basic, but that's not the point. The test's job is not to tell genius and rockstars from "normal" devs. The purpose is to save you time and quickly filter out DB-experienced guys from the ones that just claim to be.

The test

We prepared a simple database schema and ask the following questions

  1. List employees (names) who have a bigger salary than their boss
  2. List employees who have the biggest salary in their departments
  3. List departments that have less than 3 people in it
  4. List all departments along with the number of people there (tricky - people often do an "inner join" leaving out empty departments)
  5. List employees that don't have a boss in the same department
  6. List all departments along with the total salary there

Like I said, it's very basic. And there's more than one correct solution for each of these questions.

Feel free to use it in your interviews. A link back would be much appreciated ;) but not required.


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