The CData Cmdlets PowerShell Module for MYOB 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 SaleInvoices.ID, Contacts.* FROM SaleInvoices INNER JOIN Contacts ON SaleInvoices.CustomerID = Contacts.ID

Left Join

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

SELECT Jobs.ID, Contacts.* FROM Jobs LEFT JOIN Contacts ON Jobs.LinkedCustomerID = Contacts.ID