利用类及派生类在屏幕上输出英语问好提示，其输出结果如下图所示。
-category and the use of derived classes in English output on the screen greets suggest that the output results as shown in the diagram below.
SHOW FULL COLUMNS FROM `jrk_downrecords` [ RunTime:0.001320s ]
SELECT `a`.`aid`,`a`.`title`,`a`.`create_time`,`m`.`username` FROM `jrk_downrecords` `a` INNER JOIN `jrk_member` `m` ON `a`.`uid`=`m`.`id` WHERE `a`.`status` = 1 GROUP BY `a`.`aid` ORDER BY `a`.`create_time` DESC LIMIT 10 [ RunTime:0.092064s ]
SHOW FULL COLUMNS FROM `jrk_tagrecords` [ RunTime:0.001296s ]
SELECT * FROM `jrk_tagrecords` WHERE `status` = 1 ORDER BY `num` DESC LIMIT 20 [ RunTime:0.001893s ]
SHOW FULL COLUMNS FROM `jrk_member` [ RunTime:0.001503s ]
SELECT `id`,`username`,`userhead`,`usertime` FROM `jrk_member` WHERE `status` = 1 ORDER BY `usertime` DESC LIMIT 10 [ RunTime:0.006201s ]
SHOW FULL COLUMNS FROM `jrk_searchrecords` [ RunTime:0.001600s ]
SELECT * FROM `jrk_searchrecords` WHERE `status` = 1 ORDER BY `num` DESC LIMIT 5 [ RunTime:0.003382s ]
SELECT aid,title,count(aid) as c FROM `jrk_downrecords` GROUP BY `aid` ORDER BY `c` DESC LIMIT 10 [ RunTime:0.015020s ]
SHOW FULL COLUMNS FROM `jrk_articles` [ RunTime:0.001340s ]
UPDATE `jrk_articles` SET `hits` = 1 WHERE `id` = 322394 [ RunTime:0.001295s ]
