DELETE with WHERE clause in MySQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the DELETE statement do in SQL?

The DELETE statement removes rows from a table based on a condition or all rows if no condition is specified.

beginner

Why is the WHERE clause important in a DELETE statement?

The WHERE clause limits which rows get deleted. Without it, all rows in the table will be removed.

beginner

Write a DELETE statement to remove all users with age less than 18 from a table named 'users'.

DELETE FROM users WHERE age < 18;

intermediate

What happens if you run DELETE FROM employees without a WHERE clause?

All rows in the 'employees' table will be deleted, leaving the table empty.

intermediate

Can you use multiple conditions in the WHERE clause of a DELETE statement? How?

Yes, you can combine conditions using AND, OR. For example: DELETE FROM orders WHERE status = 'cancelled' AND order_date < '2023-01-01';

What does the WHERE clause do in a DELETE statement?

A Specifies the columns to delete

B Specifies the table to delete

C Specifies which rows to delete

D Specifies the database to delete

The WHERE clause filters rows to delete based on a condition.

What happens if you omit the WHERE clause in a DELETE statement?

A Only one row is deleted

B All rows in the table are deleted

C No rows are deleted

D The table structure is deleted

Without WHERE, DELETE removes all rows from the table.

Which of the following is a correct DELETE statement to remove users named 'John'?

A DELETE FROM users WHERE name = 'John';

B REMOVE FROM users WHERE name = 'John';

C DELETE users WHERE name = 'John';

D DELETE * FROM users WHERE name = 'John';

The correct syntax is DELETE FROM table WHERE condition.

How can you delete rows where age is greater than 30 and status is 'inactive'?

A DELETE FROM table WHERE age > 30 OR status = 'inactive';

B DELETE FROM table WHERE age > 30 status = 'inactive';

C DELETE FROM table WHERE age > 30, status = 'inactive';

D DELETE FROM table WHERE age > 30 AND status = 'inactive';

Use AND to combine multiple conditions that must all be true.

Which SQL keyword is used to delete rows from a table?

A DELETE

B REMOVE

C DROP

D ERASE

DELETE is the SQL keyword to remove rows from a table.

Explain how to safely delete specific rows from a table using the DELETE statement.

Think about how to target only the rows you want to remove.

Describe what happens if you run a DELETE statement without a WHERE clause and why it can be risky.

Consider the effect on the whole table.