The CData Excel Add-In for Wave Financial 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 Invoices.Title, InvoiceItems.TotalValue FROM Invoices, InvoiceItems WHERE Invoices.Id=InvoiceItems.InvoiceId

Left Join

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

SELECT Invoices.Title, InvoiceItems.TotalValue FROM Invoices LEFT OUTER JOIN InvoiceItems ON Invoices.Id=InvoiceItems.InvoiceId