PostgreSQL IN Operator

IN

The IN operator allows you to specify a list of possible values in the WHERE clause.

The IN operator is a shorthand for multiple OR conditions.

Return all customers from 'Germany', France' or 'UK':

SELECT * FROM customers
WHERE country IN ('Germany', 'France', 'UK');

By using the NOT keyword in front of the IN operator, you return all records that are NOT any of the values in the list.

Return all customers that are NOT from 'Germany', France' or 'UK':

SELECT * FROM customers
WHERE country NOT IN ('Germany', 'France', 'UK');

You can also us a SELECT statement inside the parenthesis to return all records that are in the result of the SELECT statement.

Return all customers that have an order in the orders table:

SELECT * FROM customers
WHERE customer_id IN (SELECT customer_id FROM orders);

The result in the example above returned 89 records, that means that there are 2 customers that haven't placed any orders.

Let us check if that is correct, by using the NOT IN operator.

Return all customers that have NOT placed any orders in the orders table:

SELECT * FROM customers
WHERE customer_id NOT IN (SELECT customer_id FROM orders);