oracle実装ページングとmysql実装ページング機能

String sql = "select * from ( select t.*, ROWNUM RN from ( 
select * from tblmetadatainfo  where 1=1 ";
			if ((!"".equals(fileName)) && fileName != null) {
				sql += " and backupRealName like '%" + fileName.trim() + "%'";
			}
			if ((!"".equals(fromTime)) && fromTime != null) {
				sql += " and backupDate >= to_date('" + fromTime + " 00:00:00','yyyy-mm-dd hh24:mi:ss')";
			}
			if ((!"".equals(endTime)) && endTime != null) {
				sql += " and backupDate<= to_date('" + endTime + " 23:59:59','yyyy-mm-dd hh24:mi:ss')";
			}		
			sql += "order by  id desc  ) t  WHERE ROWNUM <= " + pagenum * 15
					+ ") WHERE RN >=" + (pagenum - 1) * 15 + " ";	

sql="select * from usertablel where userid limit " +((pageNow-1)*pageSize)+","+pageSize;