The CData Cmdlets PowerShell Module for Trello supports standard SQL joins like the following examples.

Inner Join

An inner join selects only rows from both tables that match the join condition:

SELECT b.BoardId, b.Name, p.PluginId FROM Boards b INNER JOIN BoardPlugins p ON b.BoardId = p.BoardId

Left Join

A left join selects all rows in the FROM table and only matching rows in the JOIN table:

SELECT b.BoardId, b.Name, p.PluginId FROM Boards b LEFT  JOIN BoardPlugins p ON b.BoardId = p.BoardId