# isNull


`isNull` evaluates an expression to see if it is null. If the expression is null, `isNull` returns true, and otherwise it returns false.

## Syntax


```
isNull(expression)
```

## Arguments


 *expression*   
The expression to be evaluated as null or not. It can be a field name like **address1** or a call to another function that outputs a string. 

## Return type


Boolean

## Example


The following example evaluates the sales\$1amount field for null values.

```
isNull(salesAmount)
```

The following are the given field values.

```
20.13
(null)
57.54
```

For these field values, the following values are returned.

```
false
true
false
```

The following example tests for a NULL value in an `ifelse` statement, and returns a human-readable value instead.

```
ifelse( isNull({ActiveFlag}) , 'Inactive',  'Active') 
```