Amazon Redshift will no longer support the creation of new Python UDFs starting Patch 198. Existing Python UDFs will continue to function until June 30, 2026. For more information, see the [ blog post ](https://aws.amazon.com/blogs/big-data/amazon-redshift-python-user-defined-functions-will-reach-end-of-support-after-june-30-2026/). 

# HLL\$1CARDINALITY function
<a name="r_HLL_CARDINALITY"></a>

The HLL\$1CARDINALITY function returns the cardinality of the input HLLSKETCH data type.

## Syntax
<a name="r_HLL_CARDINALITY-synopsis"></a>

```
HLL_CARDINALITY (hllsketch_expression)
```

## Argument
<a name="r_HLL_CARDINALITY-argument"></a>

 *hllsketch\$1expression*   
Any valid expression that evaluates to an HLLSKETCH type, such as a column name. The input value is the HLLSKETCH data type.

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

The HLL\$1CARDINALITY function returns a BIGINT or INT8 value.

## Examples
<a name="r_HLL_CARDINALITY-examples"></a>

The following example returns the cardinality of column `sketch` in table `hll_table`.

```
CREATE TABLE a_table(an_int INT, b_int INT);
INSERT INTO a_table VALUES (1,1), (2,1), (3,1), (4,1), (1,2), (2,2), (3,2), (4,2), (5,2), (6,2);

CREATE TABLE hll_table (sketch HLLSKETCH);
INSERT INTO hll_table select hll_create_sketch(an_int) from a_table group by b_int;

SELECT hll_cardinality(sketch) AS cardinality FROM hll_table;
cardinality
-------------
6
4
(2 rows)
```