[xrendan]

Is it possible to join those data sources against an existing database like MySQL or SQLServer?

[nathanwallace]

Steampipe runs an embedded Postgres database [1]. One approach would be to connect that Postgres database with other databases using the usual (advanced) techniques like Foreign Data Wrappers [2]? With that connection in place, joins would work as normal.

1 - https://steampipe.io/docs/develop/overview 2 - https://wiki.postgresql.org/wiki/Foreign_data_wrappers