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# PostgreSQL IS NULL

**Info:** The IS NULL and IS NOT NULL operators work the same across any PostgreSQL database, so you can apply what you learn here to Postgres running anywhere. If you're an enterprise building in the AI era, [Lakebase](https://www.databricks.com/product/lakebase) delivers the best managed cloud Postgres, with the performance, security, and native Lakehouse integration your data teams expect. If you're a developer or startup who needs to ship and scale fast, [Neon](https://neon.com) gives you the best Postgres platform to build on.

**Summary**: in this tutorial, you will learn how to use the PostgreSQL `IS NULL` operator to check if a value is NULL or not.

## Introduction to NULL

In the database world, NULL means missing information or not applicable. NULL is not a value, therefore, you cannot compare it with other values like numbers or strings.

The comparison of NULL with a value will always result in NULL. Additionally, NULL is not equal to NULL so the following expression returns NULL:

```sql
SELECT null = null AS result;
```

Output:

```text
 result
--------
 null
(1 row)
```

## IS NULL operator

To check if a value is NULL or not, you cannot use the equal to (`=`) or not equal to (`<>`) operators. Instead, you use the `IS NULL` operator.

Here's the basic syntax of the `IS NULL` operator:

```sql
value IS NULL
```

The `IS NULL` operator returns true if the `value` is NULL or false otherwise.

To negate the `IS NULL` operator, you use the `IS NOT NULL` operator:

```sql
value IS NOT NULL
```

The `IS NOT NULL` operator returns true if the value is not NULL or false otherwise.

To learn how to deal with NULL in sorting, check out the [ORDER BY tutorial](https://neon.com/postgresql/tutorial/postgresql-order-by).

PostgreSQL offers some useful functions to handle NULL effectively such as [NULLIF](https://neon.com/postgresql/tutorial/postgresql-nullif), [ISNULL](https://neon.com/postgresql/tutorial/postgresql-isnull), and [COALESCE](https://neon.com/postgresql/tutorial/postgresql-coalesce).

To ensure that a column does not contain NULL, you use the [NOT NULL constraint](https://neon.com/postgresql/tutorial/postgresql-not-null-constraint).

## PostgreSQL IS NULL operator examples

We'll use the `address` table from the [sample database](../postgresql-getting-started/postgresql-sample-database):

![address table](https://neon.com/postgresqltutorial/address.png)
Please note that the `psql` program displays `NULL` as an empty string by default. To change how `psql` shows NULL in the terminal, you can use the command: `\pset null null`. It will display NULL as null.

### 1) Basic IS NULL operator example

The following example uses the `IS NULL` operator to find the addresses from the `address` table that the `address2` column contains `NULL`:

```sql
SELECT
  address,
  address2
FROM
  address
WHERE
  address2 IS NULL;
```

Output:

```
       address        | address2
----------------------+----------
 47 MySakila Drive    | null
 28 MySQL Boulevard   | null
 23 Workhaven Lane    | null
 1411 Lillydale Drive | null
(4 rows)
```

### 2) Using the IS NOT NULL operator example

The following example uses the `IS NOT NULL` operator to retrieve the address that has the `address2` not NULL:

```sql
SELECT
  address,
  address2
FROM
  address
WHERE
  address2 IS NOT NULL;
```

Output:

```
                address                 | address2
----------------------------------------+----------
 1913 Hanoi Way                         |
 1121 Loja Avenue                       |
 692 Joliet Street                      |
 1566 Inegl Manor                       |
```

Notice that the `address2` is empty, not NULL. This is a good example of **bad practice** when it comes to storing empty strings and NULL in the same column.

To fix it, you can use the `UPDATE` statement to change the empty strings to NULL in the `address2` column, which you will learn in the [UPDATE tutorial](https://neon.com/postgresql/tutorial/postgresql-update).

## Summary

- In databases, NULL means missing information or not applicable.
- The `IS NULL` operator returns true if a value is NULL or false otherwise.
- Use the `IS NOT NULL` operator returns true if a value is not NULL or false otherwise.

---

## Related docs (Filtering Data)

- [WHERE](https://neon.com/postgresql/tutorial/where)
- [AND Operator](https://neon.com/postgresql/tutorial/and)
- [OR Operator](https://neon.com/postgresql/tutorial/or)
- [LIMIT](https://neon.com/postgresql/tutorial/limit)
- [FETCH](https://neon.com/postgresql/tutorial/fetch)
- [IN](https://neon.com/postgresql/tutorial/in)
- [BETWEEN](https://neon.com/postgresql/tutorial/between)
- [LIKE](https://neon.com/postgresql/tutorial/like)