# Scalar functions
<a name="scalar_functions"></a>

This section describes the scalar functions supported in AWS Clean Rooms Spark SQL. A scalar function is a function that takes one or more values as input and returns a single value as output. Scalar functions operate on individual rows or elements and produce a single result for each input. 

Scalar functions, such as SIZE, are different from other types of SQL functions, such as aggregate functions (count, sum, avg) and table-generating functions (explode, flatten). These other function types operate on multiple rows or generate multiple rows, whereas scalar functions work on individual rows or elements.

**Topics**
+ [SIZE function](size.md)

# SIZE function
<a name="size"></a>

The SIZE function takes an existing array, map, or string as an argument and returns a single value representing the size or length of that data structure. It doesn't create a new data structure. It's used for querying and analyzing the properties of existing data structures, rather than for creating new ones.

This function is a useful for determining the number of elements in an array or the length of a string. It can be particularly helpful when working with arrays and other data structures in SQL, because it allows you to get information about the size or cardinality of the data.

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

```
size(expr)
```

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

 *expr*  
An ARRAY, MAP, or STRING expression.

## Return type
<a name="size-return-type"></a>

The SIZE function returns an INTEGER.

## Example
<a name="size-example"></a>

In this example, the SIZE function is applied to the array `['b', 'd', 'c', 'a']`, and it returns the value `4`, which is the number of elements in the array. 

```
SELECT size(array('b', 'd', 'c', 'a'));
 4
```

In this example, the SIZE function is applied to the map `{'a': 1, 'b': 2}`, and it returns the value `2`, which is the number of key-value pairs in the map. 

```
SELECT size(map('a', 1, 'b', 2));
 2
```

In this example, the SIZE function is applied to the string `'hello world'`, and it returns the value `11`, which is the number of characters in the string. 

```
SELECT size('hello world');
11
```