WHERE clause filtering in MySQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the WHERE clause in SQL?

The WHERE clause is used to filter records and return only those rows that meet a specified condition.

beginner

How do you filter rows where the column age is greater than 30?

Use WHERE age > 30 to select rows where the age value is more than 30.

intermediate

Can the WHERE clause use multiple conditions? How?

Yes, by combining conditions with AND or OR. For example, WHERE age > 30 AND city = 'Paris'.

beginner

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

All rows from the table are returned because no filtering condition is applied.

intermediate

How do you filter rows where a column name starts with the letter 'A'?

Use the LIKE operator with a wildcard: WHERE name LIKE 'A%'.

Which SQL clause is used to filter rows based on a condition?

A SELECT

B FROM

C WHERE

D ORDER BY

The WHERE clause filters rows to return only those that meet the condition.

What does this SQL do? SELECT * FROM users WHERE age < 18;

A Selects users younger than 18

B Selects users older than 18

C Selects all users

D Selects users exactly 18 years old

The condition age < 18 filters users younger than 18.

How do you combine two conditions in a WHERE clause to require both to be true?

A Using AND

B Using NOT

C Using OR

D Using LIKE

AND requires both conditions to be true for a row to be selected.

Which operator is used to match patterns in a WHERE clause?

A BETWEEN

B LIKE

C IN

D IS NULL

LIKE is used for pattern matching with wildcards like % and _.

What will happen if you run SELECT * FROM products; without a WHERE clause?

A Returns rows with NULL values only

B Returns no rows

C Returns only one row

D Returns all rows from products

Without WHERE, all rows in the table are returned.

Explain how the WHERE clause filters data in a SQL query.

Think about how you pick only certain items from a list based on a rule.

Describe how to use multiple conditions in a WHERE clause and what logical operators you can use.

Consider how you decide if you want to buy something only if it is cheap AND new.