【单选题】
（） are used to limit the pressure in any particular portion and mainly control the pressure after the valve.
A、Relief valves
B、Check valves
C、Safety valves
D、Reducing valve
查看正确答案
A、A filter is added to the table query dynamically using ROWNUM to limit the rows to 20 percent of the total rows B、All the rows are returned to the client or middle tier but only the first 20 percent are returned to the screen or the application. C、A view is created during execution and a filter on the view limits the rows to 20 percent of the total rows. D、A TOP-N query is created to limit the rows to 20 percent of the total rows
