> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sdf.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Aggregate Functions

## `approx_count_distinct`

*Supported Signatures*

```sql theme={null}
function approx_count_distinct(bigint) returns bigint
```

[🔗 Official Documentation](https://docs.aws.amazon.com/redshift/latest/dg/c_SQL_functions.html)

## `regexp_count`

*Supported Signatures*

```sql theme={null}
function regexp_count(varchar, varchar) returns bigint
function regexp_count(varchar, varchar, bigint) returns bigint
function regexp_count(varchar, varchar, bigint, varchar) returns bigint
```

[🔗 Official Documentation](https://docs.aws.amazon.com/redshift/latest/dg/REGEXP_COUNT.html)