SQL Quest

Lessons, hints, explained solutions, the in-browser PostgreSQL editor and practice answer checks in your browser are available. Graded assessments, recorded progress from answer checks and new certificates aren't available yet.

Advanced SQL assessment

Ten demanding problems in 50 minutes, one for each advanced skill: moving averages with explicit window frames, multi-step CTE pipelines, recursive hierarchies, cohort analysis, data changes checked by the final state of the tables (UPDATE and INSERT ... ON CONFLICT), conversion funnels, reporting datasets that combine facts of different grains, rewriting slow queries into fast equivalents, and date spines that show the days and months with no activity. Every answer is graded on the public data and on a hidden copy with different rows. Pass mark 75%.

Questions
10 drawn from 20
Time
50 minutes
Pass mark
75%
Retake
after 12 hours

How it works

  • Questions are drawn at random across the skills below, easiest first. A retake avoids the questions of your previous attempt wherever the question bank has others for that skill.
  • You can run queries on the real dataset as often as you like. Answers save as you type; nothing is graded until you submit.
  • The timer is kept on the server and covers writing your answers. When time runs out, your saved answers are graded as they are.
  • A query that errors or runs longer than the grader's time limit counts as not correct. A problem on our side (for example the grader being busy) never does: the attempt stays open with your answers saved, and you can submit again.
  • Each answer is graded by results on the dataset and on a hidden copy with different rows. Afterwards you see which answers passed, with the model solution and an explanation.
  • It's open-book and not proctored.

Skills covered

  • Window frames and moving averages
  • Multi-step CTE pipelines
  • Recursive CTEs
  • Cohorts and retention
  • UPDATE
  • INSERT ... ON CONFLICT and RETURNING
  • Funnel analysis
  • Building reporting datasets
  • Rewriting queries for performance
  • Time series and date spines
Not available yet. Graded assessments aren't available yet: they need SQL Quest's server-side grader, which is switched off until its security review is complete. You can still practise every lesson and check practice answers in your browser.