单项选择题
A.JDBC-ODBC BridgeB.JDBC-Native API BridgeC.JDBC-MiddlewareD.Pure JDBC driver
A.Connection类B.Statement类C.DriverManager类D.ResultSet类
A.select *from emp where comm=nullB.select *from emp where comm< >nullC.select *from emp where comm is nullD.select *from emp where comm is not null