Which query returns students from Delhi, sorted by name?

SELECT * FROM students WHERE city = 'Delhi' ORDER BY name;

SELECT * FROM students ORDER BY name WHERE city = 'Delhi';

SELECT * WHERE city = 'Delhi' FROM students ORDER BY name;

SELECT FROM students * WHERE city = 'Delhi' SORT BY name;

You want cities that have more than 10 students. Where does the condition COUNT(*) > 10 go?

In a HAVING clause after GROUP BY city

What is the main trade-off of adding an index to a column?

Faster lookups on that column, but extra storage and slightly slower INSERT, UPDATE and DELETE

It removes duplicate values automatically

There is no cost, so every column should be indexed

Which statement about a primary key is true?

Its values must be unique and cannot be NULL, and a table has only one

A table can have several primary keys

Primary key values may repeat if they are NULL

A primary key must always be a single numeric column

What does a foreign key on orders.customer_id referencing customers.id do?

Ensures each order points to a customer that exists (referential integrity)

Makes customer_id unique in orders

Automatically creates customers when an order is added

Encrypts the customer_id column

Which statement about TRUNCATE TABLE in MySQL is true?

It removes all rows and resets the AUTO_INCREMENT counter

It can remove specific rows using a WHERE clause

It fires DELETE triggers for each row

It can always be rolled back like DELETE

What is the most reliable way to prevent SQL injection?

Use parameterised queries (prepared statements) for all user input

Hide database error messages from users

Block the word SELECT in form fields

Free SQL Quiz (MySQL) With Answers

This free SQL quiz checks the database skills every web developer needs: writing SELECT queries with WHERE and ORDER BY, join types, GROUP BY and HAVING, NULL handling, indexes, primary and foreign keys, normalisation, transactions and ACID, DELETE versus TRUNCATE and preventing SQL injection. Questions use MySQL behaviour. Answer all 12 questions, check your score, then read the explanations and revisit the MySQL guide for anything you got wrong.

Frequently asked questions

Is this quiz only for MySQL?

Most questions apply to any SQL database. Where behaviour differs, such as TRUNCATE and AUTO_INCREMENT, the quiz follows MySQL with the InnoDB engine.

Where can I practise these queries?

Install MySQL or MariaDB locally (for example through XAMPP), create a small students or orders table and run the queries yourself.

Why is SQL injection in a SQL quiz?

Because it comes from how application code builds queries. Using prepared statements is part of writing SQL safely.

SQL Quiz: 12 MySQL Questions

Frequently asked questions

Is this quiz only for MySQL?

Where can I practise these queries?

Why is SQL injection in a SQL quiz?

Want to Learn This Properly?

Frequently asked questions

Is this quiz only for MySQL?

Where can I practise these queries?

Why is SQL injection in a SQL quiz?

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