You can use the CData Power BI Connector for CSV to execute standard joins. The following examples use tables in the odata.org sample Northwind database.

Inner Join

This query returns the ContactName of every Customer who has an Order and the OrderDate.

SELECT Customers.ContactName, Orders.OrderDate 
FROM Customers, Orders
WHERE Customers.CustomerID=Orders.CustomerID

Left Join

The query below retrieves the ContactName of every Customer in the Customers table and the OrderDate for every Order that the Customer placed, if any.

SELECT Customers.ContactName, Orders.OrderDate 
FROM Customers
LEFT OUTER JOIN Orders
ON Customers.CustomerID=Orders.CustomerID