1,YYYYmmdd格式日期转换为null
看如下记录,一个能取到值,一个取不到值**
mysql> SELECT DATE_FORMAT(STR_TO_DATE(‘20150922 13:01:01’, ‘%Y%m%d %H:%m:%s’),’%H:%m’);
+————————————————————————–+
| DATE_FORMAT(STR_TO_DATE(‘20150922 13:01:01’, ‘%Y%m%d %H:%m:%s’),’%H:%m’) |
+————————————————————————–+
| 13:01 |
+————————————————————————–+
1 row in set (0.00 sec)
mysql> SELECT DATE_FORMAT(STR_TO_DATE(‘20150922 12:55:00’, ‘%Y%m%d %H:%m:%s’),’%H:%m’);
+————————————————————————–+
| DATE_FORMAT(STR_TO_DATE(‘20150922 12:55:00’, ‘%Y%m%d %H:%m:%s’),’%H:%m’) |
+————————————————————————–+
| NULL |
+————————————————————————–+
1 row in set, 1 warning (0.00 sec)
mysql>
2,查看报错信息:
mysql> show warnings;
+———+——+————————————————————————+
| Level | Code | Message |
+———+——+————————————————————————+
| Warning | 1411 | Incorrect datetime value: ‘20150922 12:55:00’ for function str_to_date |
+———+——+————————————————————————+
1 row in set (0.00 sec)
mysql>
报警说是Incorrect datetime value: ‘20150922 12:55:00’ for function str_to_date,不正确的日期格式,所以换成比较规范的日期格式
原blog地址:http://blog.csdn.net/mchdba/article/details/48719765,未经过csdn原博客博主mchdba允许,不能转载。
3,换成规范的%Y-%m-%d %H:%i:%s试试
mysql> select DATE_FORMAT(str_to_date(‘2015-09-22 13:00:01’, ‘%Y-%m-%d %H:%i:%s’),’%H:%i’);
+——————————————————————————+
| DATE_FORMAT(str_to_date(‘2015-09-22 13:00:01’, ‘%Y-%m-%d %H:%i:%s’),’%H:%i’) |
+——————————————————————————+
| 13:00 |
+——————————————————————————+
1 row in set (0.00 sec)
mysql> select DATE_FORMAT(str_to_date(‘2015-09-22 12:55:00’, ‘%Y-%m-%d %H:%i:%s’),’%H:%i’);
+——————————————————————————+
| DATE_FORMAT(str_to_date(‘2015-09-22 12:55:00’, ‘%Y-%m-%d %H:%i:%s’),’%H:%i’) |
+——————————————————————————+
| 12:55 |
+——————————————————————————+
1 row in set (0.00 sec)
mysql>
看到在规范的格式下,日期从字符串转换到日期格式,然后截取时分都是能取到值的。
参考官网地址:http://dev.mysql.com/doc/refman/5.6/en/date-and-time-functions.html#function_str-to-date
4,再次确定缩小范围,是%h的问题,将时换成大写就搞定了
再看到一个案例,将格式变成2015-09-22 13:00:01表准备格式,可以仍然取不到时分值,如下所示:
<code class="hljs asciidoc">mysql> select DATE_FORMAT(str_to_date('2015-09-22 13:00:01', '%Y-%m-%d %h:%i:%s'),'%h:%i'); +------------------------------------------------------------------------------+ | DATE_FORMAT(str_to_date('2015-09-22 13:00:01', '%Y-%m-%d %h:%i:%s'),'%h:%i') | +------------------------------------------------------------------------------+ | NULL | +------------------------------------------------------------------------------+ 1 row in set, 1 warning (0.00 sec) mysql> select DATE_FORMAT(str_to_date('2015-09-22 12:55:00', '%Y-%m-%d %h:%i:%s'),'%h:%i'); +------------------------------------------------------------------------------+ | DATE_FORMAT(str_to_date('2015-09-22 12:55:00', '%Y-%m-%d %h:%i:%s'),'%h:%i') | +------------------------------------------------------------------------------+ | 12:55 | +------------------------------------------------------------------------------+ 1 row in set (0.00 sec) mysql> </code>
那么问题在哪里呢?只能再次去官网找答案,找到http://dev.mysql.com/doc/refman/5.6/en/date-and-time-functions.html#function_get-format<br>
看到终极标准格式为:’%Y-%m-%d %H.%i.%s’,换成这个试试,看到范例中的差异在哪里了吗?就在于%H和%h的区别啊,如下所示:
<code class="hljs asciidoc"><code class="hljs asciidoc">mysql> select DATE_FORMAT(str_to_date('20150922 13:00:01', '%Y%m%d %h:%i:%s'),'%h:%i'); +--------------------------------------------------------------------------+ | DATE_FORMAT(str_to_date('20150922 13:00:01', '%Y%m%d %h:%i:%s'),'%h:%i') | +--------------------------------------------------------------------------+ | NULL | +--------------------------------------------------------------------------+ 1 row in set, 1 warning (0.00 sec) mysql> select DATE_FORMAT(str_to_date('20150922 12:55:00', '%Y%m%d %h:%i:%s'),'%h:%i'); +--------------------------------------------------------------------------+ | DATE_FORMAT(str_to_date('20150922 12:55:00', '%Y%m%d %h:%i:%s'),'%h:%i') | +--------------------------------------------------------------------------+ | 12:55 | +--------------------------------------------------------------------------+ 1 row in set (0.00 sec) mysql> </code></code>
<code class="hljs asciidoc"><strong>然后标准的日期格式为:%Y%m%d %H:%i:%s’或者%Y-%m-%d %H:%i:%s’ 都可以的,如下所示:</strong>
<code class="hljs asciidoc">select DATE_FORMAT(str_to_date(‘20150922 13:00:01’, ‘%Y%m%d %H:%i:%s’),’%H:%i’);<br>
select DATE_FORMAT(str_to_date(‘20150922 12:55:00’, ‘%Y%m%d %H:%i:%s’),’%H:%i’);

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