二叉树有一个优雅的递归指针结构，所以他们是一个很好的学习方法递归指针算法。
- Binary trees have an elegant recursive pointer structure, so they are a good way to learn recursive pointer algorithms.
SHOW FULL COLUMNS FROM `jrk_downrecords` [ RunTime:0.001411s ]
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:0.088965s ]
SHOW FULL COLUMNS FROM `jrk_tagrecords` [ RunTime:0.001243s ]
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SHOW FULL COLUMNS FROM `jrk_member` [ RunTime:0.001232s ]
SELECT `id`,`username`,`userhead`,`usertime` FROM `jrk_member` WHERE `status` = 1 ORDER BY `usertime` DESC LIMIT 10 [ RunTime:0.003580s ]
SHOW FULL COLUMNS FROM `jrk_searchrecords` [ RunTime:0.001055s ]
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SELECT aid,title,count(aid) as c FROM `jrk_downrecords` GROUP BY `aid` ORDER BY `c` DESC LIMIT 10 [ RunTime:0.015375s ]
SHOW FULL COLUMNS FROM `jrk_articles` [ RunTime:0.001435s ]
UPDATE `jrk_articles` SET `hits` = 1 WHERE `id` = 131148 [ RunTime:0.001626s ]
