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.

Skill check: Intermediate and Advanced Analytics

Eight analytical requests drawn from window functions, rankings and top-N, LAG and LEAD, running totals and frames, percentiles, period comparisons, date spines and cohorts, on Wadi Market, Mizan Cloud, Nakheel Hotels and Masar Holding. Each answer is graded on the public data and on a hidden variant, so ties, frames and edge rows have to be handled by the query, not by the numbers you happen to see.

Questions
8 drawn from 16
Time
40 minutes
Pass mark
75%
Retake
after 6 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

  • OVER and PARTITION BY
  • ROW_NUMBER, RANK, DENSE_RANK
  • Top-N per group
  • LAG and LEAD
  • Running totals
  • Window frames and moving averages
  • NTILE, percentiles and distributions
  • Period-over-period comparison
  • Time series and date spines
  • Cohorts and retention
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.