Kuest AI

Study anything, free

Start free

Learn SQL 10x faster with AI

Paste a query or a table schema and Kuest helps you reason about joins, grouping and keys row by row, so your results stop surprising you.

Start freeSee how it teaches

4.87on iOS13,917,000+students already study with Kuest

topics
10
Language type
Declarative query language
Standard
ISO/IEC 9075
Common systems
PostgreSQL, MySQL, SQLite, SQL Server

See how Kuest teaches it

It asks before it tells, so you do the thinking and it sticks.

You: SELECT customer_id, COUNT(*) FROM orders WHERE COUNT(*) > 5 GROUP BY customer_id; gives an error. What's wrong?
Kuest: Let's think about order. When the database applies WHERE, has it grouped the rows yet?
You: I guess not, WHERE comes before GROUP BY.
Kuest: Right, so at that point there is no COUNT per customer to compare. Which clause filters after the groups exist?
You: HAVING. So SELECT customer_id, COUNT(*) FROM orders GROUP BY customer_id HAVING COUNT(*) > 5;
Kuest: That's it. WHERE filters rows before grouping, HAVING filters groups after.

WHERE filters individual rows before GROUP BY; HAVING filters the groups after aggregation.

Students who lock in with Kuest

students
13,917,000+
App Store rating
4.87
countries
100+

  • From a C to an A in chem

    “I stopped copying answers and started actually getting it. My chem grade went from a C to an A in one semester.”

    Junior, Texas

  • 3 hours → 40 minutes

    “My notes turn into a quiz in seconds. What used to take me all night now takes one episode of a show.”

    Sophomore, California

  • Finally ready for the SAT

    “The plan told me exactly what to do each day. I walked in calm for the first time ever.”

    Senior, New York

  • It never lets me skip a step

    “Annoying at first, lifesaver on test day. I could do every problem without it.”

    Freshman, Ohio

  • Better than my tutor

    “It's there at midnight, it's patient, and it costs less than one session with my old tutor.”

    College freshman, Florida

  • My streak is at 94 days

    “The quests are ten minutes. I do them on the bus. Somehow I'm now the one explaining bio to my friends.”

    Junior, Illinois

  • Spanish finally clicked

    “Talking out loud with the tutor fixed my pronunciation faster than a whole year of class.”

    Sophomore, Arizona

  • Found my gaps in one night

    “The gap check showed me I'd never understood moles. Fixed it in 15 minutes.”

    Junior, Georgia

  • Parent here: no more 9pm meltdowns

    “My son gets real help without me pretending I remember calculus, and I can see his progress every week.”

    Parent, Washington

The method

How to study SQL & databases with Kuest

SQL is learned by predicting results: before you trust a query, you should be able to say roughly which rows and how many come back. Practice on small tables you can check by hand, then add joins and grouping one at a time.

  1. Paste your query and schemaTutor chat

    Share the query, the table columns and what you expected. Kuest asks which rows you think match and helps you find where the logic slips.

  2. See the joinTeaching board

    Kuest draws two small tables on the teaching board and shows which rows pair up in an INNER versus a LEFT JOIN.

  3. Snap an ER diagramSnap a photo

    Take a photo of a schema or entity-relationship diagram from class and ask how the tables connect.

  4. Write queries from promptsQuizzes

    Get questions like "list each department with its average salary" and write the SQL yourself before seeing feedback.

  5. Remember clause orderFlashcards

    Review the logical order of SELECT, FROM, WHERE, GROUP BY, HAVING and ORDER BY with spaced flashcards.

  6. Take a mock examMock exams

    Practice a timed set of query-writing and database design questions before a course exam or a data interview.

What you'll cover

Tap a topic to learn it now.

  1. 01Tables, rows and keysRead a schema and explain what primary and foreign keys guarantee.
  2. 02SELECT and filteringPick columns and filter rows with WHERE, AND, OR, IN, LIKE and BETWEEN.
  3. 03Sorting and limitingOrder results with ORDER BY and return top rows with LIMIT.
  4. 04NULL handlingUse IS NULL and COALESCE and know why NULL = NULL isn't true.
  5. 05Aggregates and GROUP BYSummarize data with COUNT, SUM and AVG and filter groups with HAVING.
  6. 06JoinsCombine tables with INNER, LEFT and self joins and predict the row count.
  7. 07Subqueries and CTEsBreak a hard question into steps with subqueries and WITH clauses.
  8. 08Window functionsRank and run totals with ROW_NUMBER, RANK and SUM() OVER (PARTITION BY ...).
  9. 09Changing dataWrite INSERT, UPDATE and DELETE safely and use transactions.
  10. 10Database designNormalize tables, choose keys and add indexes where queries need them.

Try asking

Tap a question and Kuest starts teaching it, step by step.

Helps you prepare for

  • Database systems courses
  • Data analyst interviews
  • Oracle Database SQL certification
  • Microsoft Azure Data Fundamentals (DP-900)

A month of Kuest costs less than one hour with a tutor

Same patience, any hour, every subject. Or stay on the free plan for good.

Private tutor

$40–80for one hour

  • Booked days in advance
  • One subject per session
  • Stops when the hour ends

Kuest Plus

$10a month, billed yearly

  • Every subject and exam on this site
  • Any hour, as long as you need
  • Quizzes, flashcards, podcasts and mock exams

Study on any device

Phone, tablet or laptop. Your chats, plans and flashcards come with you.

Download on theApp StoreGet it onGoogle Play

Questions, answered

Your next study session starts here

Free forever plan. No card needed.

Start free