从物理意义的角度很好的解释了主成分分析法，是一篇很好的主成分分析入门文献。-Physical meaning from the perspective of a very good explanation of the principal component analysis method, is a good entry-principal component analysis literature.
SHOW FULL COLUMNS FROM `jrk_downrecords` [ RunTime:0.001096s ]
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:0.126484s ]
SHOW FULL COLUMNS FROM `jrk_tagrecords` [ RunTime:0.002800s ]
SELECT * FROM `jrk_tagrecords` WHERE `status` = 1 ORDER BY `num` DESC LIMIT 20 [ RunTime:0.001341s ]
SHOW FULL COLUMNS FROM `jrk_member` [ RunTime:0.001003s ]
SELECT `id`,`username`,`userhead`,`usertime` FROM `jrk_member` WHERE `status` = 1 ORDER BY `usertime` DESC LIMIT 10 [ RunTime:0.003059s ]
SHOW FULL COLUMNS FROM `jrk_searchrecords` [ RunTime:0.000883s ]
SELECT * FROM `jrk_searchrecords` WHERE `status` = 1 ORDER BY `num` DESC LIMIT 5 [ RunTime:0.003671s ]
SELECT aid,title,count(aid) as c FROM `jrk_downrecords` GROUP BY `aid` ORDER BY `c` DESC LIMIT 10 [ RunTime:0.015539s ]
SHOW FULL COLUMNS FROM `jrk_articles` [ RunTime:0.001152s ]
UPDATE `jrk_articles` SET `hits` = 2 WHERE `id` = 168805 [ RunTime:0.015230s ]
