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PostgreSQL IN

Summary: in this tutorial, you will learn how to use the PostgreSQL IN operator to check if a value matches any value in a list.

Introduction to PostgreSQL IN operator​

The IN operator allows you to check whether a value matches any value in a list of values.

Here’s the basic syntax of the IN operator:

value IN (value1,value2,...)

The IN operator returns true if the value is equal to any value in the list such as value1 and value2.

The list of values can be a list of literal values including numbers and strings.

In addition to literal values, the IN operator also accepts a list of values returned from a query. You’ll learn more about how to use the IN operator with a query in the subquery tutorial.

Functionally, the IN operator is equivalent to combining multiple boolean expressions with the OR operators:

value = value1 OR value = value2 OR ...

PostgreSQL IN operator examples​

We’ll use the film table from the sample database:

1) Using the PostgreSQL IN operator with a list of numbers​

The following example uses the IN operator to retrieve information about the film with id 1, 2, and 3:

SELECT
  film_id,
  title
FROM
  film
WHERE
  film_id in (1, 2, 3);

Output:

 film_id |      title
---------+------------------
       1 | Academy Dinosaur
       2 | Ace Goldfinger
       3 | Adaptation Holes
(3 rows)

The following statement uses the equal (=) and OR operators instead of the IN operator, which is equivalent to the query above:

SELECT
  film_id,
  title
FROM
  film
WHERE
  film_id = 1
  OR film_id = 2
  OR film_id = 3;

The query that uses the IN operator is shorter and more readable than the query that uses equal (=) and OR operators.

Additionally, PostgreSQL executes the query with the IN operator much faster than the same query that uses a list of OR operators.

2) Using the PostgreSQL IN operator with a list of strings​

We’ll use the actor table from the sample database:

The following example uses the IN operator to find the actors who have the last name in the list 'Allen', 'Chase', and 'Davis':

SELECT
  first_name,
  last_name
FROM
  actor
WHERE
  last_name IN ('Allen', 'Chase', 'Davis')
ORDER BY
  last_name;

Output:

 first_name | last_name
------------+-----------
 Meryl      | Allen
 Cuba       | Allen
 Kim        | Allen
 Jon        | Chase
 Ed         | Chase
 Susan      | Davis
 Jennifer   | Davis
 Susan      | Davis
(8 rows)

3) Using the PostgreSQL IN operator with a list of dates​

The following statement uses the IN operator to find payments whose payment dates are in a list of dates: 2007-02-15 and 2007-02-16:

SELECT
  payment_id,
  amount,
  payment_date
FROM
  payment
WHERE
  payment_date::date IN ('2007-02-15', '2007-02-16');

Output:

payment_id | amount |        payment_date
------------+--------+----------------------------
      17503 |   7.99 | 2007-02-15 22:25:46.996577
      17504 |   1.99 | 2007-02-16 17:23:14.996577
      17505 |   7.99 | 2007-02-16 22:41:45.996577
      17512 |   4.99 | 2007-02-16 00:10:50.996577
...

In this example, the payment_date column has the type timestamp that consists of both date and time parts.

To match the values in the payment_date column with a list of dates, you need to cast them to date values that have the date part only.

To do that you use the :: cast operator:

payment_date::date

For example, if the timestamp value is 2007-02-15 22:25:46.996577, the cast operator will convert it to 2007-02-15.

PostgreSQL NOT IN operator​

To negate the IN operator, you use the NOT IN operator. Here’s the basic syntax of the NOT IN operator:

value NOT IN (value1, value2, ...)

The NOT IN operator returns true if the value is not equal to any value in the list such as value1 and value2; otherwise, the NOT IN operator returns false.

The NOT IN operator is equivalent to a combination of multiple boolean expressions with the AND operators:

value <> value1 AND value <> value2 AND ...

PostgreSQL NOT IN operator example​

The following example uses the NOT IN operator to retrieve films whose id is not 1, 2, or 3:

SELECT
  film_id,
  title
FROM
  film
WHERE
  film_id NOT IN (1, 2, 3)
ORDER BY
  film_id;

Output:

 film_id |            title
---------+-----------------------------
       4 | Affair Prejudice
       5 | African Egg
       6 | Agent Truman
       7 | Airplane Sierra
       8 | Airport Pollock
...

The following query retrieves the same set of data but uses the not-equal (<>) and AND operators:

SELECT
  film_id,
  title
FROM
  film
WHERE
  film_id <> 1
  AND film_id <> 2
  AND film_id <> 3
ORDER BY
  film_id;

Summary​

  • Use the IN operator to check if a value matches any value in a list of values.
  • Use the NOT operator to negate the IN operator.