The CData ADO.NET Provider for Highrise 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 charges.amount, customers.email FROM customers INNER JOIN charges ON charges.customerId = customers.id

Left Join

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

SELECT charges.amount, customers.email FROM customers LEFT JOIN charges ON charges.customerId = customers.id