AND, OR, NOT logical operators in MySQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the AND operator do in a SQL WHERE clause?

The AND operator combines two conditions and returns true only if both conditions are true.

beginner

How does the OR operator work in SQL?

The OR operator returns true if at least one of the combined conditions is true.

beginner

Explain the NOT operator in SQL.

The NOT operator reverses the result of a condition. If the condition is true, NOT makes it false, and vice versa.

intermediate

Write a SQL query using AND and OR to find employees who are in department 10 and have a salary over 5000 or are in department 20.

SELECT * FROM employees WHERE (department_id = 10 AND salary > 5000) OR department_id = 20;

intermediate

Why is it important to use parentheses when combining AND and OR in SQL?

Parentheses control the order of evaluation, ensuring the query logic works as intended by grouping conditions properly.

Which SQL operator returns true only if both conditions are true?

A AND

B OR

C NOT

D BETWEEN

AND returns true only when both conditions are true.

What does the OR operator do in SQL?

A Checks for equality

B Returns true if both conditions are false

C Negates a condition

D Returns true if at least one condition is true

OR returns true if at least one condition is true.

How does the NOT operator affect a condition?

A It makes the condition always true

B It combines two conditions

C It reverses the condition's result

D It checks if a value is null

NOT reverses the result of a condition.

Which query correctly finds rows where age is over 30 AND city is 'New York'?

A SELECT * FROM table WHERE age > 30 AND city = 'New York';

B SELECT * FROM table WHERE age > 30 OR city = 'New York';

C SELECT * FROM table WHERE NOT age > 30 AND city = 'New York';

D SELECT * FROM table WHERE age > 30 NOT city = 'New York';

AND requires both conditions to be true.

Why use parentheses in a WHERE clause with AND and OR?

A To make the query run faster

B To group conditions and control evaluation order

C To comment out parts of the query

D To format the query for readability only

Parentheses group conditions to control how SQL evaluates them.

Describe how AND, OR, and NOT logical operators work in SQL WHERE clauses.

Think about how these operators combine or change conditions.

Explain why parentheses are important when using AND and OR together in SQL queries.

Consider how math uses parentheses to clarify operations.