HardSQL challenge #225WINDOW FUNCTIONPERCENTILERANKING

Calculate Salary Percentile Rank with PERCENT_RANK()

Return each salary with its relative position between 0 and 1.

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

Assign percentile rank to salaries.

A correct answer returns 120 rows with 2 columns: salary, pct.

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
salarypct
460440
503600.008403361344537815
504630.01680672268907563
514650.025210084033613446
521640.03361344537815126

First 5 of 120 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

  • Expressing a row's position as a fraction with PERCENT_RANK()

Hint and approach

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

Show the hint

PERCENT_RANK()

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. Compute PERCENT_RANK(), the relative position from 0 to 1, ordered by salary.

Model solution

Checking your session…

What to watch for

PERCENT_RANK() is (rank - 1) / (rows - 1): the lowest salary scores 0 and the highest scores 1. CUME_DIST() is the variant that answers what share of rows are at or below this one, and never returns 0.

  • PERCENT_RANK(). PERCENT_RANK() returns a value between 0 and 1, not a percentage. Multiply by 100 to display it as one.
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Same technique, other tables

More practice on this pattern with different columns:

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