# Functions

> Provides an overview of the SQL functions available in GreptimeDB, including categories and examples of their usage.

# Functions

Use this page as a quick index to GreptimeDB function references.

## Function References

- [DataFusion Functions](./df-functions.md)
- GreptimeDB Functions
  - [Core Functions (string, math, date/time, system, admin)](./greptimedb.md)
  - [Geospatial Functions](./geo.md)
  - [IP Functions](./ip.md)
  - [JSON Functions](./json.md)
  - [Vector Functions](./vector.md)
  - [Approximate Functions](./approximate.md)
  - [Anomaly Detection Functions](./anomaly.md)