IN and NOT IN operators in MySQL

Introduction

IN and NOT IN help you find rows where a value matches or does not match any value in a list. They make checking multiple values easy and quick.

You want to find customers from specific cities like 'New York', 'Chicago', or 'Los Angeles'.

You want to exclude products that are in certain categories from your results.

You want to check if a student's grade is one of several passing grades.

You want to filter orders that belong to a set of order IDs.

You want to find employees who are not in a list of managers.

Syntax

MySQL

SELECT column_name(s) FROM table_name WHERE column_name IN (value1, value2, ...);

SELECT column_name(s) FROM table_name WHERE column_name NOT IN (value1, value2, ...);

The list inside IN or NOT IN is a set of values separated by commas and enclosed in parentheses.

IN checks if the value matches any in the list; NOT IN checks if it matches none.

Examples

Finds all employees who work in either Sales or Marketing departments.

MySQL

SELECT * FROM employees WHERE department IN ('Sales', 'Marketing');

Finds products that are not in Electronics or Toys categories.

MySQL

SELECT * FROM products WHERE category NOT IN ('Electronics', 'Toys');

Finds students whose grade is A, B, or C.

MySQL

SELECT name FROM students WHERE grade IN ('A', 'B', 'C');

Sample Program

This creates a simple employees table, adds four employees, then selects names of employees in Sales or Marketing departments, and then those not in these departments.

MySQL

CREATE TABLE employees (
  id INT,
  name VARCHAR(50),
  department VARCHAR(50)
);

INSERT INTO employees VALUES
(1, 'Alice', 'Sales'),
(2, 'Bob', 'HR'),
(3, 'Charlie', 'Marketing'),
(4, 'Diana', 'IT');

SELECT name FROM employees WHERE department IN ('Sales', 'Marketing');

SELECT name FROM employees WHERE department NOT IN ('Sales', 'Marketing');

Important Notes

If the list in IN or NOT IN is empty, the query may return no rows or all rows depending on the operator.

NULL values in the list or column can affect results; be careful when NULLs are involved.

IN and NOT IN are easier to read and write than multiple OR or AND conditions.

Summary

IN checks if a value matches any value in a list.

NOT IN checks if a value does not match any value in a list.

They simplify queries that need to compare against multiple values.

Practice

1. What does the IN operator do in a MySQL query?

easy

A. Checks if a value is greater than all values in a list

B. Checks if a value is less than all values in a list

C. Checks if a value matches any value in a list

D. Checks if a value is equal to a single value only

Solution

1. Step 1: Understand the purpose of IN operator

   The IN operator is used to test if a value exists within a set of values.

2. Step 2: Compare with other options

   The options describing comparisons with all values (greater or less than all) are incorrect, as IN checks if a value matches any in the list. The option about equality to a single value is also wrong, since IN handles multiple values.

3. Final Answer:

   Checks if a value matches any value in a list -> Option C

4. Quick Check:

   IN operator = check value in list [OK]

Hint: IN means "is in this list"; NOT IN means "not in this list" [OK]

Common Mistakes:

• Confusing IN with equality (=) operator
• Thinking IN checks all values instead of any
• Mixing IN with greater than or less than comparisons

2. Which of the following is the correct syntax to select rows where the column status is either 'active', 'pending', or 'closed'?

easy

A. SELECT * FROM table WHERE status IN ('active', 'pending', 'closed');

B. SELECT * FROM table WHERE status = IN ('active', 'pending', 'closed');

C. SELECT * FROM table WHERE status NOT IN ('active', 'pending', 'closed');

D. SELECT * FROM table WHERE status IN 'active', 'pending', 'closed';

Solution

1. Step 1: Check correct IN syntax

   The correct syntax uses IN followed by parentheses containing a comma-separated list of values.

2. Step 2: Identify errors in other options

   SELECT * FROM table WHERE status = IN ('active', 'pending', 'closed'); has an extra '=' which is invalid. SELECT * FROM table WHERE status NOT IN ('active', 'pending', 'closed'); uses NOT IN which selects rows not matching the list. SELECT * FROM table WHERE status IN 'active', 'pending', 'closed'; misses parentheses around the list.

3. Final Answer:

   SELECT * FROM table WHERE status IN ('active', 'pending', 'closed'); -> Option A

4. Quick Check:

   Correct IN syntax uses parentheses and no '=' [OK]

Hint: IN must be followed by parentheses with values inside [OK]

Common Mistakes:

• Using '=' before IN
• Omitting parentheses around the list
• Confusing IN with NOT IN

3. Given the table employees with a column department, what will this query return?

SELECT name FROM employees WHERE department NOT IN ('HR', 'Finance');

medium

A. Names of employees in HR or Finance departments

B. Names of employees not in HR or Finance departments

C. Names of employees only in HR department

D. Syntax error due to NOT IN usage

Solution

1. Step 1: Understand NOT IN operator

   NOT IN selects rows where the column value is not in the given list.

2. Step 2: Apply to the query context

   The query returns employee names whose department is not 'HR' or 'Finance'.

3. Final Answer:

   Names of employees not in HR or Finance departments -> Option B

4. Quick Check:

   NOT IN excludes listed values [OK]

Hint: NOT IN excludes listed values from results [OK]

Common Mistakes:

• Thinking NOT IN returns only listed values
• Confusing NOT IN with IN
• Assuming syntax error with NOT IN

4. Identify the error in this query:

SELECT * FROM orders WHERE order_status NOT IN 'shipped', 'delivered';

medium

A. Missing parentheses around the list after NOT IN

B. Incorrect use of NOT IN instead of IN

C. order_status should be in quotes

D. No error, query is correct

Solution

1. Step 1: Check syntax of NOT IN usage

   NOT IN must be followed by parentheses containing the list of values.

2. Step 2: Identify missing parentheses

   The query lists values without parentheses, causing syntax error.

3. Final Answer:

   Missing parentheses around the list after NOT IN -> Option A

4. Quick Check:

   NOT IN requires parentheses around values [OK]

Hint: Always use parentheses after IN or NOT IN [OK]

Common Mistakes:

• Omitting parentheses around value list
• Using quotes incorrectly around column names
• Confusing IN and NOT IN usage

5. You want to find customers who have placed orders but exclude those from countries 'USA', 'Canada', and 'Mexico'. Which query correctly uses NOT IN to achieve this?

hard

A. SELECT customer_id FROM orders WHERE country != ('USA', 'Canada', 'Mexico');

B. SELECT customer_id FROM orders WHERE country IN ('USA', 'Canada', 'Mexico');

C. SELECT customer_id FROM orders WHERE country NOT IN 'USA', 'Canada', 'Mexico';

D. SELECT customer_id FROM orders WHERE country NOT IN ('USA', 'Canada', 'Mexico');

Solution

1. Step 1: Understand the goal

   We want customers excluding those from USA, Canada, and Mexico.

2. Step 2: Choose correct NOT IN syntax

   SELECT customer_id FROM orders WHERE country NOT IN ('USA', 'Canada', 'Mexico'); uses NOT IN with parentheses and a list, correctly excluding those countries.

3. Step 3: Identify errors in other options

   SELECT customer_id FROM orders WHERE country IN ('USA', 'Canada', 'Mexico'); includes those countries (wrong). SELECT customer_id FROM orders WHERE country NOT IN 'USA', 'Canada', 'Mexico'; misses parentheses (syntax error). SELECT customer_id FROM orders WHERE country != ('USA', 'Canada', 'Mexico'); uses != with a list, which is invalid syntax.

4. Final Answer:

   SELECT customer_id FROM orders WHERE country NOT IN ('USA', 'Canada', 'Mexico'); -> Option D

5. Quick Check:

   NOT IN with parentheses excludes listed values [OK]

Hint: Use NOT IN with parentheses to exclude multiple values [OK]

Common Mistakes:

• Using != with multiple values
• Omitting parentheses after NOT IN
• Confusing IN and NOT IN