spam留言知几何之二

今天晚上，教Julia学习数据库玩。
去后台查了一下本站的留言板数据库，发现spam留言依然肆虐。
整个网站，除了被攻击时损失了部分数据，现在有效的回复只有不到2000条:

mysql> select count(*) from guestbook;
+----------+
| count(*) |
+----------+
| 1944 |
+----------+
1 row in set (0.00 sec)

而垃圾留言呢?有近2000条:

mysql> select count(*) from spambook;
+----------+
| count(*) |
+----------+
| 17787 |
+----------+
1 row in set (0.00 sec)

如果我没有采取过滤措施，那么可以想象，留言板一定早已经面目全非了。
真是佩服这些无聊人士每天废寝忘食的四处散布垃圾信息:

mysql> select FROM_UNIXTIME(dateline,'%Y-%m-%d') 'date' ,count(*)    
    -> from spambook group by 1 order by 1 desc limit 20;
+------------+----------+
| date       | count(*) |
+------------+----------+
| 2006-09-23 | 2        |
| 2006-09-22 | 75       |
| 2006-09-21 | 98       |
| 2006-09-20 | 106      |
| 2006-09-19 | 90       |
| 2006-09-18 | 125      |
| 2006-09-17 | 106      |
| 2006-09-16 | 142      |
| 2006-09-15 | 111      |
| 2006-09-14 | 125      |
| 2006-09-13 | 110      |
| 2006-09-12 | 115      |
| 2006-09-11 | 123      |
| 2006-09-10 | 112      |
| 2006-09-09 | 127      |
| 2006-09-08 | 100      |
| 2006-09-07 | 116      |
| 2006-09-06 | 96       |
| 2006-09-05 | 112      |
| 2006-09-04 | 122      |
+------------+----------+
20 rows in set (0.14 sec)

让我们见识一下Top100的无聊人士都有哪些: