INNER JOIN in MySQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does an INNER JOIN do in SQL?

An INNER JOIN returns only the rows where there is a match in both tables based on the join condition.

beginner

Write the basic syntax of an INNER JOIN between two tables table1 and table2 on column id.

SELECT * FROM table1 INNER JOIN table2 ON table1.id = table2.id;

beginner

If a row in table1 has no matching row in table2, will it appear in the INNER JOIN result?

No, only rows with matching values in both tables appear in the INNER JOIN result.

intermediate

How is INNER JOIN different from LEFT JOIN?

INNER JOIN returns only matching rows in both tables, while LEFT JOIN returns all rows from the left table and matching rows from the right table (or NULL if no match).

intermediate

Can you use INNER JOIN to join more than two tables?

Yes, you can chain multiple INNER JOINs to combine more than two tables by specifying join conditions for each pair.

What rows does an INNER JOIN return?

A Only rows with matching values in both tables

B All rows from the left table

C All rows from the right table

D All rows from both tables

INNER JOIN returns only rows where the join condition matches in both tables.

Which keyword can replace INNER JOIN and produce the same result?

A OUTER JOIN

B LEFT JOIN

C JOIN

D CROSS JOIN

JOIN by itself is the same as INNER JOIN in SQL.

What happens if there is no matching row in the second table for INNER JOIN?

A The row is excluded from the result

B The row is duplicated

C An error occurs

D The row from the first table is included with NULLs

INNER JOIN excludes rows without matches in both tables.

Which clause specifies the condition for an INNER JOIN?

A WHERE

B ON

C GROUP BY

D HAVING

The ON clause defines the join condition for INNER JOIN.

Can INNER JOIN be used to join tables on multiple columns?

A Only with subqueries

B No, only one column can be used

C Only with UNION

D Yes, by specifying multiple conditions in ON

You can join on multiple columns by adding conditions combined with AND in the ON clause.

Explain in your own words what an INNER JOIN does and when you would use it.

Think about matching pairs in two lists.

Describe the difference between INNER JOIN and LEFT JOIN with an example scenario.

Imagine a guest list and RSVP responses.