INNER JOIN with ON condition in SQL - 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 specified condition.

beginner

What is the purpose of the ON condition in an INNER JOIN?

The ON condition specifies how to match rows from the two tables, usually by comparing columns with related data.

beginner

Write a simple INNER JOIN query to get matching rows from tables Employees and Departments where Employees.DepartmentID equals Departments.ID.

SELECT * FROM Employees INNER JOIN Departments ON Employees.DepartmentID = Departments.ID;

beginner

If an INNER JOIN query returns zero rows, what does it mean about the data?

It means there are no matching rows between the two tables based on the ON condition.

intermediate

Can you use multiple conditions in the ON clause of an INNER JOIN? How?

Yes, you can combine multiple conditions using AND or OR inside the ON clause to match rows more precisely.

What does the ON clause specify in an INNER JOIN?

A How to match rows between tables

B Which columns to select

C The order of rows in the result

D The database to use

The ON clause tells SQL how to find matching rows between the two tables.

What rows does an INNER JOIN return?

A All rows from the first table

B Only rows with matching values in both tables

C All rows from the second table

D All rows from both tables

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

Which SQL keyword is used to combine rows from two tables based on a condition?

A INNER JOIN

B GROUP BY

C ORDER BY

D WHERE

INNER JOIN combines rows from two tables based on the ON condition.

Can the ON condition use more than one column to match rows?

A No, only one column is allowed

B Only in LEFT JOIN

C Yes, by using AND or OR to combine conditions

D Only if the columns have the same name

You can combine multiple conditions in the ON clause using AND or OR.

If you want to join tables but keep all rows from the first table even if no match exists, should you use INNER JOIN?

A No, use CROSS JOIN

B Yes, INNER JOIN keeps all rows from the first table

C Yes, but only with ON condition

D No, use LEFT JOIN instead

INNER JOIN only returns matching rows; LEFT JOIN keeps all rows from the first table.

Explain in your own words what an INNER JOIN with an ON condition does.

Think about how you find common friends between two groups.

Write a simple INNER JOIN query example and describe what it returns.

Use two example tables like Employees and Departments.