[[esql-is_null]]
=== `IS_NULL`
Returns a boolean than indicates whether its input is `null`.

[source,esql]
----
FROM employees
| WHERE IS_NULL(first_name)
----

Combine this function with `NOT` to filter out any `null` data:

[source,esql]
----
FROM employees
| WHERE NOT IS_NULL(first_name)
----
