private void LoadQuerySimple()
{
UnionSubQuery unionSubQuery = _query.QueryRoot.FirstSelect();
// add three objects to the query
DataSource ds1 = _query.AddObject(unionSubQuery, "MyDB.MySchema.Customers", "c");
DataSource ds2 = _query.AddObject(unionSubQuery, "MyDB.MySchema.Orders", "o");
DataSource ds3 = _query.AddObject(unionSubQuery, "MyDB.MySchema.Resellers", "r");
// create a relation between 'Resellers' and 'Orders'
_query.AddLink(ds3, "ResellerID", ds2, "ResellerID");
// create WHERE condition
QueryColumnListItem ci2 = unionSubQuery.QueryColumnList.AddExpression("CustomerID");
// do not add this item to the select list
ci2.Selected = false;
ci2.ConditionStrings[0] = "> 0";
// create an output column
QueryColumnListItem ci3 = unionSubQuery.QueryColumnList.AddField(ds1, "CustomerName");
// add this item to the select list
ci3.Selected = true;
}