# GTFS DuckDB: Functions

Every function for working with GTFS data, in five groups, each with an example that runs on the MBTA subway feed.

Page: /docs/gtfs-duckdb/functions/

## Groups

- [Import](/docs/gtfs-duckdb/functions/import.md): Load a GTFS feed and manage the dataset built from it. (21 functions)
- [Table functions](/docs/gtfs-duckdb/functions/tables.md): Whole-feed tables: one row per station, stop, route, trip or service. (7 functions)
- [GTFS functions](/docs/gtfs-duckdb/functions/gtfs.md): Look up one station, pathway network, route or trip. (23 functions)
- [Helpers](/docs/gtfs-duckdb/functions/helpers.md): Scalar functions for any SQL expression: GTFS times and codes to readable values. (7 functions)
- [For fun](/docs/gtfs-duckdb/functions/for-fun.md): Turn a day's schedule into music: a note for every stop and every departure. (5 functions)

33 more functions are internal (caches, map bounds and filter menus for GTFS Viz's maps, and helpers behind other functions) and are not covered here.