How many questions are in this quiz?

This quiz has 129 questions on INNER, LEFT, and FULL joins.

What join types does the quiz focus on?

It focuses on INNER JOIN, LEFT (OUTER) JOIN, and FULL (OUTER) JOIN behavior and outputs.

No. Every question has 4 options and there is no timer, so you can work at your own pace.

How is the difficulty balanced?

Difficulty is mixed, combining basics with edge cases like NULL handling, filters after joins, and row multiplication.

Can I choose the number of questions and difficulty?

Yes. You can select your preferred question count and difficulty before starting to match your study goals.

SQL Joins: Inner, Left, Full Quiz

About this quiz

What you’ll learn in this SQL joins quiz

INNER, LEFT, and FULL joins can look simple until you have to predict the exact output. This quiz helps you build confidence by turning join theory into repeatable, testable outcomes.

Each question uses a 4-option multiple-choice format with no timer, so you can slow down and reason through the rows before you pick an answer.

Difficulty and question count options

Difficulty is mixed on purpose: you’ll see straightforward join identification alongside trickier cases involving NULLs, filtering, and unmatched rows. Choose your preferred question count and difficulty before you start to tailor the session to quick practice or deeper revision.

Common pitfalls to watch for

Putting conditions on the wrong side of a LEFT JOIN and accidentally turning it into an INNER JOIN
Using WHERE filters that remove NULL-extended rows after an outer join
Confusing FULL JOIN behavior with UNION or expecting duplicates to be removed
Misreading join keys when there are multiple matches (row multiplication)
Forgetting how NULL values behave in join comparisons

Tips to improve your accuracy

Before answering, mentally list which table is “preserved” (for LEFT/FULL) and where NULLs can appear. Then estimate the row count first, and only after that focus on the specific columns returned.