2009-10-04 157 views
3

谁能告诉我为什么会发生以下情况,以及如何解决它?MySQL查询疯狂?

我有与订单MySQL查询BY子句,看起来像这样..

ORDER BY (did_voteup-did_votedown) DESC, did_voteup DESC 

因此,应当责令其通过“有效”的评级结果,如..

1st. 10 up - 1 down = 9 effective 
2nd. 10 up - 5 down = 5 effective 
3rd. 10 up - 7 down = 3 effective 

然而,正如你可以看到my page here,它命令他们错了,给我这个..

1st. 1 up - 3 down = -2 effective 
2nd. 16 up - 6 down = 10 effective 
3rd. 15 up - 5 down = 10 effective 

显然,那第一个地方的行不应该在那里。


更多信息..

CREATE TABLE dictionary_definitions (
    did_id int(11) unsigned NOT NULL auto_increment, 
    did_wordid int(11) unsigned NOT NULL default '0', 
    did_userid int(11) unsigned NOT NULL default '0', 
    did_status tinyint(1) unsigned NOT NULL default '0', 
    did_date int(11) NOT NULL default '0', 
    did_definition text, 
    did_example text, 
    did_votecheck int(11) NOT NULL default '0', 
    did_voteup smallint(5) unsigned NOT NULL default '0', 
    did_votedown smallint(5) unsigned NOT NULL default '0', 
    PRIMARY KEY (did_id), 
    KEY (did_wordid), 
    KEY (did_userid) 
) ENGINE=MyISAM; 

SELECT a.did_id, a.did_userid, a.did_definition, a.did_example, 
    a.did_votecheck, a.did_voteup, a.did_votedown, b.user_name, b.user_extra8 
FROM dictionary_definitions AS a LEFT JOIN users AS b ON a.did_userid=b.user_id 
WHERE did_wordid=4 
ORDER BY (did_voteup-did_votedown) DESC, did_voteup DESC LIMIT 0, 5 
+1

什么是整个查询? – scottm 2009-10-04 22:30:22

+0

看起来像数据类型的问题,请你能显示整个查询和表的结构吗? – 2009-10-04 22:32:24

+1

正如大卫所说,如果该字段是一个字符串,它会把1,10,2类型的疯狂。 – Deverill 2009-10-04 22:41:49

回答

8

这是一个众所周知issue regarding subtraction from unsigned integers

整数值之间的减法,其中一个是UNSIGNED类型,默认情况下会生成一个无符号的 结果。如果结果否则会成为最大整数值。如果启用了NO_UNSIGNED_SUBTRACTION SQL模式,则结果为 为负数。

参考:Numeric Types