# NULL Handling

Unless otherwise noted, NULL handling is as defined in the SQL standard; the result of a comparison with NULL is NULL, which, when used to qualify rows, is treated as false.

## IS NULL, IS NOT NULL

`IS NULL` and `IS NOT NULL` are postfix operators; the argument appears on the left. They return true if the argument is NULL or NOT NULL, respectively. For example:

```sql
CREATE TABLE n_s(b BOOLEAN, t TEXT);
INSERT n_s VALUES(true, "blue"), (false, "red"), (true, NULL);

```

```sql
SELECT * FROM n_s WHERE t IS NULL;

```

```output

+------+------+
| b    | t    |
+------+------+
|    1 | NULL |
+------+------+
```

```sql
SELECT 'x' IS NULL, NULL IS NULL, NULL IS NOT NULL;

```

```output

+-------------+--------------+------------------+
| 'x' IS NULL | NULL IS NULL | NULL IS NOT NULL |
+-------------+--------------+------------------+
|           0 |            1 |                0 |
+-------------+--------------+------------------+

```

## ISNULL()

The `ISNULL()` function behaves the same as IS NULL except it uses the standard function syntax where the single argument appears on the right, e.g. `ISNULL(expr)` returns true if `expr` is NULL and false otherwise.

## NULL-safe equal operator: `<=>`

The NULL-safe equal operator, `<=>` returns `true` if both arguments are NULL. Otherwise, it is the same as the `=` operator. For example:

```sql
SELECT * FROM n_s AS s1, n_s AS s2 WHERE s1.t <=> s2.t;

```

```output

+------+------+------+------+
| b    | t    | b    | t    |
+------+------+------+------+
|    1 | blue |    1 | blue |
|    1 | NULL |    1 | NULL |
|    0 | red  |    0 | red  |
+------+------+------+------+

```

***

Modified at: February 28, 2023

Source: [/db/v9.1/reference/sql-reference/comparison-operators-and-functions/null-handling/](https://docs.singlestore.com/db/v9.1/reference/sql-reference/comparison-operators-and-functions/null-handling/)

(An index of the documentation is available at /llms.txt)