给出集合类的定义，可模拟实现集合的交集，并集运算，并可以插入，删除元素-is set class definition can be simulated to achieve the intersection and set computing, and can be inserted, deleted elements
SHOW FULL COLUMNS FROM `jrk_downrecords` [ RunTime:0.001346s ]
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:0.093645s ]
SHOW FULL COLUMNS FROM `jrk_tagrecords` [ RunTime:0.001262s ]
SELECT * FROM `jrk_tagrecords` WHERE `status` = 1 ORDER BY `num` DESC LIMIT 20 [ RunTime:0.002241s ]
SHOW FULL COLUMNS FROM `jrk_member` [ RunTime:0.001342s ]
SELECT `id`,`username`,`userhead`,`usertime` FROM `jrk_member` WHERE `status` = 1 ORDER BY `usertime` DESC LIMIT 10 [ RunTime:0.003878s ]
SHOW FULL COLUMNS FROM `jrk_searchrecords` [ RunTime:0.001135s ]
SELECT * FROM `jrk_searchrecords` WHERE `status` = 1 ORDER BY `num` DESC LIMIT 5 [ RunTime:0.003786s ]
SELECT aid,title,count(aid) as c FROM `jrk_downrecords` GROUP BY `aid` ORDER BY `c` DESC LIMIT 10 [ RunTime:0.015876s ]
SHOW FULL COLUMNS FROM `jrk_articles` [ RunTime:0.001526s ]
UPDATE `jrk_articles` SET `hits` = 1 WHERE `id` = 283222 [ RunTime:0.001540s ]
