You can construct a query SQL statement to query data from a local database. This query may across multiple tables (MBOs).
Query query2 = new Query();
query2.select("c.fname,c.lname,s.order_date,s.region");
query2.from("Customer", "c");
//
// Convenience method for adding a join to the query
// Detailed construction of the join criteria
query2.join("Sales_order", "s", "c.id", "s.cust_id");
AttributeTest ts = new AttributeTest();
ts.setAttribute("fname");
ts.setTestValue("Beth");
query2.where(ts);
QueryResultSet qrs = SampleAppDB.executeQuery(query2);