The CData Power BI Connector for Confluence 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 Pages.Title, Spaces.Name FROM Contents, Spaces WHERE Pages.SpaceKey=Spaces.Key

Left Join

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

SELECT Pages.Title, Spaces.Name FROM Contents LEFT OUTER JOIN Spaces ON Pages.SpaceKey=Spaces.Key