# Null data functions
<a name="sql-functions-null"></a>

 Null data functions handle or manipulate NULL values, which represent the absence of a value. The functions allow you to replace NULLs with other values, check if a value is NULL, or perform operations that handle NULLs in a specific way. 


|  **Function**  |  **Signature**  |  **Description**  | 
| --- | --- | --- | 
|  `COALESCE`  |   COALESCE (expression1, expression2, ..., expressionN)   |  If all expressions evaluate to null, COALESCE returns null. Expressions must be of same type.  | 

**Example of a COALESCE function**  

```
SELECT COALESCE (l.double_value, 100) AS non_double_value FROM latest_value_time_series AS l LIMIT 1
```