MySQL中DATE_FORMATE函数内置字符集解析
发布:smiling 来源: PHP粉丝网 添加日期:2014-09-25 15:59:32 浏览: 评论:0
今天在利用DATE_FORMATE处理两个日期判断时发现提示 Illegal mix of collations (utf8_general_ci,COERCIBLE),这个是字符集问题呀,但我是日期怎么会这样,当时没看到,后来看到一篇文章才想起来,下面我们一起来看看解决办法.
处理一个SQL,简化过后的执行报错,代码如下:
- mysql> select date_format('2013-11-19','Y-m-d') > timediff('2013-11-19', '2013-11-20');
- ERROR 1267 (HY000): Illegal mix of collations (utf8_general_ci,COERCIBLE) and (latin1_swedish_ci,NUMERIC) for operation '>'
乍一看挺莫名其妙的,查了下手册,发现有这么一段:
The language used for day and month names and abbreviations is controlled by the value of the lc_time_names system variable (Section 9.7, “MySQL Server Locale Support”).
The DATE_FORMAT() returns a string with a character set and collation given by character_set_connection and collation_connection so that it can return month and weekday names containing non-ASCII characters.
也就是说,DATE_FORMATE() 函数返回的结果是带有字符集/校验集属性的,而 TIMEDIFF() 函数则没有字符集/校验集属性,我们来验证一下,代码如下:
- mysql> set names utf8;
- mysql> select charset(date_format('2013-11-19','Y-m-d')), charset(timediff('2013-11-19', '2013-11-20'));
- +--------------------------------------------+-----------------------------------------------+
- | charset(date_format('2013-11-19','Y-m-d')) | charset(timediff('2013-11-19', '2013-11-20')) |
- +--------------------------------------------+-----------------------------------------------+
- | utf8 | binary |
- +--------------------------------------------+-----------------------------------------------+
- mysql> set names gb2312;
- mysql> select charset(date_format('2013-11-19','Y-m-d')), charset(timediff('2013-11-19', '2013-11-20'));
- +--------------------------------------------+-----------------------------------------------+
- | charset(date_format('2013-11-19','Y-m-d')) | charset(timediff('2013-11-19', '2013-11-20')) |
- +--------------------------------------------+-----------------------------------------------+//开源代码phpfensi.com
- | gb2312 | binary |
- +--------------------------------------------+-----------------------------------------------+
可以看到,随着通过 SET NAMES 修改 character_set_connection、collation_connection 值,DATE_FORMAT() 函数返回结果的字符集也跟着不一样,在这种情况下,想要正常工作,就需要将结果进行一次字符集转换,代码如下:
- mysql> select date_format('2013-11-19','Y-m-d') > convert(timediff('2013-11-19', '2013-11-20') using utf8);
- +----------------------------------------------------------------------------------------------+
- | date_format('2013-11-19','Y-m-d') > convert(timediff('2013-11-19', '2013-11-20') using utf8) |
- +----------------------------------------------------------------------------------------------+
- | 1 |
- +----------------------------------------------------------------------------------------------+
就可以了.
P.S,MySQL的版本:5.5.20-55-log Percona Server (GPL), Release rel24.1,Revision 217.
附后,下面是函数的参数说明:
Tags: DATE_FORMATE MySQL字符集解析
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