In the Service Explorer, in the context menu of the OrderService service, choose Add Operation.

For Operation Type, select Query. For Name, enter getItemsByOrderId. For Description, enter This query returns all items of a given order. (The order is identified by its order ID.)

Choose Next.

Choose Add input.

Choose Add.

For Name, enter pi_orderid. For Type, enter string.

Choose OK.

Choose Add output, select OrderOrderItem, and choose OK.

Choose Add filter.

In the top two dropdown boxes, select OrderOrderItem and OrderId. In the middle dropdown box, select = (equals). In the bottom two dropdown boxes, select, From Input Parameter and pi_orderid.

Choose OK.

Choose Finish.

Save your work.

In the Services Explorer, in the context menu of the order_srv component, choose  Development Component Build and then OK.