# IS\$1NULL expression
<a name="IS_NULL"></a>

The IS\$1NULL conditional expression is used to check if a value is null.

This expression is a synonym for IS NULL.

## Syntax
<a name="IS_NULL-syntax"></a>

```
is_null(expr)
```

## Arguments
<a name="IS_NULL-arguments"></a>

*expr*  
An expression of any type.

## Returns
<a name="IS_NULL-returns"></a>

The IS\$1NULL conditional expression returns a Boolean. If `expr1` is NULL, returns `true`, otherwise returns `false`.

## Examples
<a name="IS_NULL-example"></a>

The following example checks if the value `1` is null, and returns the boolean result `true` because 1 is a valid, non-null value.

```
SELECT is not null(1);
 true
```

The following example selects the `id` column from the `squirrels` table, but only for the rows where the age column is `null`.

```
SELECT id FROM squirrels WHERE is_null(age)
```