# Derived Columns

Calculated Fields (also called Derived Columns) allow you to run queries based on the value of an expression that is derived from the fields in an event.

This API allows you to list, create, update, and delete Calculated Fields in a dataset or across a whole environment, paralleling the behavior of the Schema tab within a Dataset's or Environment's Settings UI.



## Create a Derived Column

 - [POST /1/derived_columns/{datasetSlug}](https://api-docs.honeycomb.io/api/derived-columns/createderivedcolumn.md): Create a Calculated Field (also called a Derived Column). Calculated Fields allow you to run queries based on the value of an expression that is derived from the columns in an event.


## List all Derived Columns

 - [GET /1/derived_columns/{datasetSlug}](https://api-docs.honeycomb.io/api/derived-columns/listderivedcolumns.md): Get all the Calculated Fields (also called Derived Columns) in a dataset or environment. With the  query parameter, can return a single Calculated Field by its .

## Get a Derived Column

 - [GET /1/derived_columns/{datasetSlug}/{derivedColumnId}](https://api-docs.honeycomb.io/api/derived-columns/getderivedcolumn.md)

## Update a Derived Column

 - [PUT /1/derived_columns/{datasetSlug}/{derivedColumnId}](https://api-docs.honeycomb.io/api/derived-columns/updatederivedcolumn.md): Update a Calculated Field (also called a Derived Column).


## Delete a Derived Column

 - [DELETE /1/derived_columns/{datasetSlug}/{derivedColumnId}](https://api-docs.honeycomb.io/api/derived-columns/deletederivedcolumn.md): Delete a Calculated Field (also called a Derived Column). : A Calculated Field used by a SLO, Trigger, or Board cannot be deleted without removing or modifying the SLO, Trigger, or Board first.