SELECT A.*,IFNULL(B.`Name`,'') AS VisitorName,C.ClassDate,C.ClassTime,C.EndTime,C.ClassContent,IFNULL(D.TeacherName,'') AS TeacherName,IFNULL(E.RoomName,'') AS RoomName
FROM RB_Visitor_Reserve AS A LEFT JOIN rb_visitor AS B ON A.Visitor_Id=B.Id
SELECT A.*,IFNULL(B.StuName,'') AS VisitorName,C.ClassDate,C.ClassTime,C.EndTime,C.ClassContent,IFNULL(D.TeacherName,'') AS TeacherName,IFNULL(E.RoomName,'') AS RoomName
FROM RB_Visitor_Reserve AS A LEFT JOIN rb_student AS B ON A.Visitor_Id=B.StuId
LEFT JOIN rb_reserve_class AS C ON A.ReserveClassId=C.ReserveClassId
LEFT JOIN rb_teacher AS D ON C.TeacherId=D.TId
LEFT JOIN rb_class_room AS E ON C.ClassRoomId=E.RoomId