# String functions
<a name="sql-functions-string"></a>

 String functions are built-in tools used to manipulate and process text data. They enable tasks like concatenation, extraction, formatting, and searching within strings. These functions are essential for cleaning, transforming, and analyzing text-based data within a database. 


**String functions**  

|  **Function**  |  **Signature**  |  **Description**  | 
| --- | --- | --- | 
| `LENGTH` |  LENGTH (string)  | Returns the length of the string. | 
| `CONCAT` |  CONCAT (string, string)  | Concatenates arguments in a string. | 
| `SUBSTR` |  [See the AWS documentation website for more details](http://docs.aws.amazon.com/iot-sitewise/latest/userguide/sql-functions-string.html)  | Returns one of the following:[See the AWS documentation website for more details](http://docs.aws.amazon.com/iot-sitewise/latest/userguide/sql-functions-string.html)<br />Uses 1-based indexing for start parameter. | 
| `UPPER` |  UPPER (string)  | Converts the characters in the input string to uppercase. | 
| `LOWER` |  LOWER (string)  | Converts the characters in the input string to lowercase. | 
| `TRIM` |  TRIM (string)  | Removes any space characters from the beginning, end, or both sides of string. | 
| `LTRIM` |  LTRIM (string)  | Removes any space characters from the beginning of string. | 
| `RTRIM` |  RTRIM (string)  | Removes any space characters from the end of string. | 
| `STR_REPLACE` |  STR\_REPLACE (string, from, to)  | Replaces all occurrences of the specified substring with another specified substring. | 

Examples of all the functions:


|  **Function**  |  **Example**  | 
| --- | --- | 
| LENGTH | `SELECT LENGTH(a.asset_id) AS asset_id_length FROM asset AS a` | 
| CONCAT |  `SELECT CONCAT(p.property_id, p.property_name) FROM asset_property AS p`  | 
| SUBSTR |  [See the AWS documentation website for more details](http://docs.aws.amazon.com/iot-sitewise/latest/userguide/sql-functions-string.html)  | 
| UPPER |  `SELECT UPPER(d.string_value) AS up_string FROM raw_time_series AS d`  | 
| LOWER |  `SELECT LOWER(d.string_value) AS low_string FROM raw_time_series AS d`  | 
| TRIM |  `SELECT TRIM(d.string_value) AS tm_string FROM raw_time_series AS d`  | 
| LTRIM |  `SELECT LTRIM(d.string_value) AS ltrim_string FROM raw_time_series AS d`  | 
| RTRIM |  `SELECT RTRIM(d.string_value) AS rtrim_string FROM raw_time_series AS d`  | 
| STR\_REPLACE |  `SELECT STR_REPLACE(d.string_value, 'abc', 'def') AS replaced_string FROM raw_time_series AS d`  | 

## Concatenation operator
<a name="sql-operators-concatenation"></a>

 The concatenation operator `||`, or pipe operator, joins two strings together. It provides an alternative to the `CONCAT` function, and is more readable when combining multiple strings.

**Example of the concatenation operator**  

```
SELECT a.asset_name || ' - ' || p.property_name 
  AS full_name
  FROM asset a, asset_property p
```