DELETE with WHERE condition in SQL - 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 specified condition. Without a condition, it deletes all rows.

beginner

Why is the WHERE clause important in a DELETE statement?

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

beginner

Write a DELETE statement to remove all users older than 30 from a table named Users.

DELETE FROM Users WHERE age > 30;

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 but still existing.

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 this SQL do? DELETE FROM Products WHERE price < 10;

A Deletes all products with price less than 10

B Deletes all products with price greater than 10

C Deletes all products

D Deletes the Products table

The WHERE clause limits deletion to rows where price is less than 10.

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

A Deletes all rows in the table

B Deletes no rows

C Deletes only the first row

D Deletes the table structure

Without WHERE, DELETE removes every row from the table.

Which keyword is used to specify which rows to delete?

A ORDER BY

B FROM

C SELECT

D WHERE

WHERE defines the condition to select rows for deletion.

How do you delete rows where the column 'status' equals 'inactive'?

A DELETE * FROM table WHERE status = 'inactive';

B DELETE status FROM table;

C DELETE FROM table WHERE status = 'inactive';

D REMOVE FROM table WHERE status = 'inactive';

Correct syntax uses DELETE FROM with WHERE condition.

Can you delete rows based on multiple conditions?

A No, only one condition is allowed

B Yes, using AND or OR in WHERE clause

C Yes, but only with OR

D Yes, but only with AND

Multiple conditions can be combined with AND or OR in WHERE.

Explain how the DELETE statement works with a WHERE condition in SQL.

Think about deleting specific items from a list by setting rules.

Describe the risks of running a DELETE statement without a WHERE clause and how to avoid them.

Consider what happens if you clear your entire contact list by mistake.