EasySQL challenge #74GROUP BYMAX

Get the Maximum Salary per Department with GROUP BY

Return each department with its highest salary.

The challenge runs on the SQLabHub practice database (SQLite) and uses the employees table. You can solve it in the browser, with nothing to install.

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The task

Find highest salary in each department.

A correct answer returns 10 rows with 2 columns: department, MAX(salary).

Tables used in this challenge

employees 120 rows

id INTEGER (PK) · first_name TEXT · last_name TEXT · email TEXT · department TEXT · department_id INTEGER · title TEXT · salary REAL · hire_date TEXT · manager_id INTEGER · city TEXT · status TEXT

First 3 rows of the employees table
idfirst_namelast_nameemaildepartmentdepartment_idtitlesalaryhire_datemanager_idcitystatus
1WilliamLewiswlewis18@corp.ioCustomer Success7Senior CS Manager617742022-07-24NULLSan Diegoactive
2JohnMillerjmiller51@corp.ioLegal8Paralegal1916942021-08-09NULLSan Diegoactive
3DanielRiveradrivera50@corp.ioEngineering1VP Engineering1350672016-06-06NULLHoustonactive

The first rows of each table are shown. See how all the tables relate on the database schema page.

Expected output

Expected output of the challenge
departmentMAX(salary)
Customer Success203999
Design194543
Engineering199029
Finance196032
HR191037
Legal192220
Marketing204449
Operations203467
Product188273
Sales195759

The complete result: 10 rows. This is the output of the model solution on the practice database. The task does not fix a sort order, so your rows may come back in a different order.

What you practise

  • Summarising many rows into one value with COUNT, SUM, AVG, MIN or MAX
  • Grouping rows with GROUP BY to get one result row per group

Hint and approach

Try the challenge first. Open these only when you need them.

Show the hint

GROUP BY department

Show the step-by-step approach

How the model solution is built, in the order the database evaluates it:

  1. Read from the employees table.
  2. Group the rows by department, so the result has one row for each value.
  3. For each group, compute MAX(salary).

Model solution

Checking your session…

What to watch for

This returns the top salary figure for each department, not the person who earns it. Adding first_name to the SELECT list picks an arbitrary employee in SQLite and is an error in most other databases.

  • GROUP BY. Every selected column must either be in GROUP BY or sit inside an aggregate. SQLite accepts other columns and returns an arbitrary value for them; most databases raise an error.
  • Aggregate functions. Aggregates skip NULLs. AVG divides by the number of non-NULL values and COUNT(column) can be smaller than COUNT(*).
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Same technique, other tables

More practice on this pattern with different columns:

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