WHERE with IN list in SQL

Introduction

The WHERE with IN list helps you find rows where a column matches any value from a list. It makes checking many values easy and fast.

You want to find customers from a few specific cities.

You need to get orders with certain status codes.

You want to filter products that belong to several categories.

You want to check if an employee's department is one of a few departments.

You want to select students who are in a list of classes.

Syntax

SQL

SELECT column1, column2, ...
FROM table_name
WHERE column_name IN (value1, value2, value3, ...);

The list inside IN is a set of values to match.

Values can be numbers or strings (strings need quotes).

Examples

Selects employees who work in department 1, 2, or 3.

SQL

SELECT * FROM employees WHERE department_id IN (1, 2, 3);

Finds products in either 'Books' or 'Toys' categories.

SQL

SELECT name FROM products WHERE category IN ('Books', 'Toys');

Checks orders with status exactly 'Pending'. This is like using = but with IN list.

SQL

SELECT * FROM orders WHERE status IN ('Pending');

This is an empty list. It returns no rows because no city matches nothing.

SQL

SELECT * FROM customers WHERE city IN ();

Sample Program

This creates a simple employees table, adds four employees, then selects those in departments 1, 3, or 5.

SQL

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

INSERT INTO employees (id, name, department_id) VALUES
(1, 'Alice', 1),
(2, 'Bob', 2),
(3, 'Charlie', 3),
(4, 'Diana', 4);

-- Find employees in departments 1, 3, or 5
SELECT id, name, department_id FROM employees WHERE department_id IN (1, 3, 5);

Important Notes

The IN list makes queries shorter and easier than many OR conditions.

Using a large list in IN can slow down the query; consider joins or temporary tables for big lists.

Remember that IN checks for exact matches; it does not work like LIKE or partial matches.

Summary

WHERE with IN list filters rows by matching a column to any value in a list.

It is easier and cleaner than writing many OR conditions.

Use it when you have a fixed set of values to check against.

Practice

1. What does the SQL clause WHERE column_name IN (value1, value2, value3) do?

easy

A. It selects rows where column_name matches any value in the list.

B. It updates rows with values in the list.

C. It deletes rows not matching the list.

D. It creates a new table with listed values.

Solution

1. Step 1: Understand the IN clause purpose

   The IN clause checks if a column's value matches any value inside the parentheses list.

2. Step 2: Identify the effect on row selection

   Rows with the column value equal to any listed value are selected; others are ignored.

3. Final Answer:

   It selects rows where column_name matches any value in the list. -> Option A

4. Quick Check:

   WHERE with IN filters rows by listed values [OK]

Hint: IN checks if value matches any in the list [OK]

Common Mistakes:

• Thinking IN updates or deletes rows
• Confusing IN with creating tables
• Assuming IN matches all values at once

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

easy

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

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

C. SELECT * FROM orders WHERE status IN 'active', 'pending', 'closed';

D. SELECT * FROM orders WHERE status IN ('active' 'pending' 'closed');

Solution

1. Step 1: Check correct use of IN syntax

   The correct syntax is column_name IN (value1, value2, ...) without an equals sign.

2. Step 2: Identify correct punctuation and parentheses

   Values must be inside parentheses and separated by commas.

3. Final Answer:

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

4. Quick Check:

   IN syntax = column IN (values) [OK]

Hint: No '=' before IN; use commas inside parentheses [OK]

Common Mistakes:

• Using '=' before IN
• Missing commas between values
• Omitting parentheses around values

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

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

medium

A. Rows where department is 'HR' or 'Sales'.

B. Rows where department is 'HR' only.

C. Rows where department is not 'HR' or 'Sales'.

D. All rows regardless of department.

Solution

1. Step 1: Understand the IN filter on department

   The query filters rows where department matches any value in ('HR', 'Sales').

2. Step 2: Determine which rows match

   Only rows with department 'HR' or 'Sales' are returned; others are excluded.

3. Final Answer:

   Rows where department is 'HR' or 'Sales'. -> Option A

4. Quick Check:

   IN filters rows matching listed values [OK]

Hint: IN returns rows matching any listed value [OK]

Common Mistakes:

• Thinking it returns rows not in the list
• Assuming it returns only one value
• Confusing IN with NOT IN

4. Identify the error in this SQL query:

SELECT * FROM products WHERE category IN 'Electronics', 'Toys', 'Books';

medium

A. Incorrect table name.

B. Using IN instead of = operator.

C. Missing parentheses around the list of values.

D. Missing commas between values.

Solution

1. Step 1: Check syntax of IN clause

   The list of values after IN must be enclosed in parentheses.

2. Step 2: Identify missing parentheses

   The query has values listed without parentheses, causing syntax error.

3. Final Answer:

   Missing parentheses around the list of values. -> Option C

4. Quick Check:

   IN requires parentheses around values [OK]

Hint: Always put parentheses around IN value list [OK]

Common Mistakes:

• Omitting parentheses around values
• Using IN with equals sign
• Forgetting commas between values

5. You want to select customers from the orders table whose country is either 'USA', 'Canada', or 'Mexico', but exclude those with status 'cancelled'. Which query correctly uses WHERE with IN and excludes cancelled orders?

hard

A. SELECT * FROM orders WHERE country IN 'USA', 'Canada', 'Mexico' AND status != 'cancelled';

B. SELECT * FROM orders WHERE country IN ('USA', 'Canada', 'Mexico') OR status != 'cancelled';

C. SELECT * FROM orders WHERE country = IN ('USA', 'Canada', 'Mexico') AND status != 'cancelled';

D. SELECT * FROM orders WHERE country IN ('USA', 'Canada', 'Mexico') AND status != 'cancelled';

Solution

1. Step 1: Use IN correctly for country filter

   The country column must be checked with IN ('USA', 'Canada', 'Mexico') without equals sign.

2. Step 2: Exclude cancelled orders with AND condition

   Use AND status != 'cancelled' to exclude those rows.

3. Final Answer:

   SELECT * FROM orders WHERE country IN ('USA', 'Canada', 'Mexico') AND status != 'cancelled'; -> Option D

4. Quick Check:

   IN filters list, AND excludes cancelled [OK]

Hint: Use AND to combine IN filter and exclusion [OK]

Common Mistakes:

• Using OR instead of AND causing wrong results
• Adding '=' before IN
• Omitting parentheses around IN values