# CARDINALITY function
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The CARDINALITY function returns the size of an ARRAY or MAP expression (*expr*).

This function is useful to find the size or length of an array.

## Syntax
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```
cardinality(expr)
```

## Arguments
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 *expr*   
An ARRAY or MAP expression.

## Returns
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Returns the size of an array or a map (INTEGER). 

The function returns `NULL` for null input if `sizeOfNull` is set to `false` or `enabled` is set to `true`. 

Otherwise, the function returns `-1` for null input. With the default settings, the function returns `-1` for null input.

## Example
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The following query calculates the cardinality, or the number of elements, in the given array. The array (`'b', 'd', 'c', 'a'`) has 4 elements, so the output of this query would be `4`.

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