单表查询（所有字段）

SelectQuery sel = OQL   .Select(NW.Order)   .From(NW.Order)   .Where(OQL     .Criteria(NW.Order.EmployeeID).EQ(5)     .And(NW.Order.ShipVia).EQ(1)   );

== SQL for MS Sql Server ==

SELECT [Orders].* FROM [Orders] WHERE   [Orders].[EmployeeID] = 5 AND   [Orders].[ShipVia] = 1

== SQL for Oracle ==

SELECT "Orders".* FROM "Orders" WHERE   "Orders"."EmployeeID" = 5 AND   "Orders"."ShipVia" = 1

单表查询（列举字段）

SelectQuery sel = OQL   .Select(NW.Order.OrderID, NW.Order.OrderDate, NW.Order.RequiredDate)   .From(NW.Order)   .Where(NW.Order.EmployeeID == 5 & NW.Order.ShipVia == 1);

== SQL for MS Sql Server ==

SELECT   [Orders].[OrderID] , [Orders].[OrderDate] , [Orders].[RequiredDate] FROM [Orders] WHERE   [Orders].[EmployeeID] = 5 AND   [Orders].[ShipVia] = 1

多表查询

SelectQuery sel = OQL   .Select(NW.Order.OrderID, NW.Order.OrderDate, NW.Order.RequiredDate)     ._(NW.OrderDetail)   .From(NW.Order, NW.OrderDetail)   .Where(NW.Order.EmployeeID == 5 & NW.Order.ShipVia == 1     & NW.Order.OrderID == NW.OrderDetail.OrderID);

== SQL for MS Sql Server ==

SELECT   [Orders].[OrderID] , [Orders].[OrderDate] , [Orders].[RequiredDate] ,   [Order Details].* FROM   [Orders] , [Order Details] WHERE   [Orders].[EmployeeID] = 5 AND   [Orders].[ShipVia] = 1 AND   [Orders].[OrderID] = [Order Details].[OrderID]

多表Join查询

SelectQuery sel = OQL   .Select(NW.Order.OrderID, NW.Order.OrderDate, NW.Order.RequiredDate)     ._(NW.OrderDetail)   .From(NW.Order)   .InnerJoin(NW.OrderDetail)     .On(NW.Order.OrderID == NW.OrderDetail.OrderID)   .Where(NW.Order.EmployeeID == 5     && NW.Order.ShipVia == 1   );

== SQL for MS Sql Server ==

SELECT   [Orders].[OrderID] , [Orders].[OrderDate] , [Orders].[RequiredDate] ,   [Order Details].* FROM [Orders]   INNER JOIN     [Order Details]     ON       [Orders].[OrderID] = [Order Details].[OrderID] WHERE   [Orders].[EmployeeID] = 5 AND   [Orders].[ShipVia] = 1

子查询

SelectQuery sel = OQL   .Select(NW.Order.OrderID, NW.Order.OrderDate, NW.Order.RequiredDate)   .From(NW.Order)   .Where(NW.Order.CustomerID.In(OQL       .Select(NW.Customer.CustomerID)       .From(NW.Customer)       .Where(NW.Customer.ContactTitle == "Owner")     )   );

== SQL for MS Sql Server ==

SELECT   [Orders].[OrderID] , [Orders].[OrderDate] , [Orders].[RequiredDate] FROM [Orders] WHERE   [Orders].[CustomerID] IN     (       SELECT [Customers].[CustomerID]       FROM [Customers]       WHERE         [Customers].[ContactTitle] = 'Owner'     )

子查询（分解）

SelectQuery subSel = OQL   .Select(NW.Customer.CustomerID)   .From(NW.Customer)   .Where(NW.Customer.ContactTitle == "Owner");   SelectQuery sel = OQL   .Select(NW.Order.OrderID, NW.Order.OrderDate, NW.Order.RequiredDate)   .From(NW.Order)   .Where(NW.Order.CustomerID.In(subSel));

== SQL for MS Sql Server ==

SELECT   [Orders].[OrderID] , [Orders].[OrderDate] , [Orders].[RequiredDate] FROM [Orders] WHERE   [Orders].[CustomerID] IN     (       SELECT [Customers].[CustomerID]       FROM [Customers]       WHERE         [Customers].[ContactTitle] = 'Owner'     )