WHERE with IN list in SQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the SQL WHERE ... IN clause do?

It filters rows to include only those where a column's value matches any value in a specified list.

beginner

Write a simple example of a WHERE ... IN clause.

SELECT * FROM employees WHERE department IN ('Sales', 'Marketing');<br>This returns employees in either Sales or Marketing departments.

intermediate

Can the IN list contain numbers and strings together?

No, the list should contain values of the same data type as the column being filtered.

beginner

How is WHERE ... IN different from multiple OR conditions?

WHERE column IN (a, b, c) is a shorter, clearer way to write WHERE column = a OR column = b OR column = c.

intermediate

What happens if the IN list is empty?

The query returns no rows because no value can match an empty list.

What does this SQL do? <br>SELECT * FROM products WHERE category IN ('Books', 'Toys');

A Selects all products except Books and Toys

B Selects products not in Books or Toys categories

C Selects products with category NULL

D Selects products only in Books or Toys categories

The IN clause filters rows to those where category is either 'Books' or 'Toys'.

Which is equivalent to WHERE id IN (1, 2, 3)?

A WHERE id = 1 AND id = 2 AND id = 3

B WHERE id NOT IN (1, 2, 3)

C WHERE id = 1 OR id = 2 OR id = 3

D WHERE id > 1 AND id < 3

IN with multiple values is like OR conditions for equality.

What data type should the values in the IN list match?

A The same data type as the column

B Any data type

C Only strings

D Only numbers

Values in the IN list must match the column's data type for correct filtering.

What result do you get if the IN list is empty?

A No rows returned

B All rows returned

C Error in SQL syntax

D Returns NULL values only

An empty IN list matches no values, so no rows are returned.

Which is a benefit of using WHERE ... IN over multiple OR conditions?

A It runs slower

B It is easier to read and write

C It only works with numbers

D It returns more rows

IN makes queries shorter and clearer compared to many OR conditions.

Explain how the WHERE ... IN clause works in SQL and give a simple example.

Think about choosing items from a list.

Describe the difference between using WHERE ... IN and multiple OR conditions.

Consider how you write the conditions.