Various examples are directed to systems and methods for managing a database to include data from an external data source. A database engine may receive a request to add a reference column to a database described by a database schema. The request may comprise a location parameter describing a location of the external data source comprising data for populating the reference column and a data identifying parameter describing data at the external data source for populating the reference column. The database engine may modify the database schema to include the reference column, send a query to the external data source to obtain at least one data item for populating the reference column, and populate the reference column with the at least one data item.