:orphan:

.. _in:

**************************
IN
**************************

``IN`` is used to test if an expression is contained in a list of values.

This is also known as set membership.

Syntax
==========

.. code-block:: postgres

   expr [ NOT ] IN  ( value_expr [, ...] )
   


Arguments
============

.. list-table:: 
   :widths: auto
   :header-rows: 1
   
   * - Parameter
     - Description
   * - ``expr``
     - A general value expression or a literal to test.
   * - ``value_expr [, ...]``
     - A comma separated list of literal values of the same data type as ``expr``

Returns
============

Returns ``TRUE`` when ``expr`` is contained in the set, or ``FALSE`` otherwise.


Notes
=======

* ``NULL`` is never equal to ``NULL``, so to check if a value is ``NULL`` use :ref:`IS NULL<is_null>` instead.

* Using ``IN`` with more than 100 literal values can slow down query compilation. If your query relies on more than 100 values, consider using a lookup table and an inner join.

Examples
===========

IN
-----------

.. code-block:: psql

   farm=> SELECT name, num_eyes FROM cool_animals WHERE num_eyes IN (8, 10)
   name           | num_eyes
   ---------------+---------
   Spider         |        8
   Horseshoe crab |       10


NOT IN
--------------

.. code-block:: psql

   farm=> SELECT name, num_eyes FROM cool_animals WHERE num_eyes NOT IN (8, 10)
   name           | num_eyes
   ---------------+---------
   Box Jellyfish  |       24
   Human          |        2
   Fox            |        2
   Possum         |        2