varchar m：d：Y H：i：s到mysql的日期和日期时间格式转换

Question

  

我使用phpmyadmin，我已将varchar（modefied_date）转换为日期   和datetime formate一样 varchar column ＆＃39; 26-12-2017 12：21：12＆＃39;到日期   ＆＃39; 2017年12月26日＆＃39;和日期时间＆＃39; 2017-12-26 12：21：12＆＃39;

     

locatio_table

id modefied_date         location
----------------------------------
1  26-12-2017 12:21:12   salem
2  26-12-2017 12:26:52   erode
3  26-12-2017 12:32:12   coimbatore

modefied_date是varchar data_type

我尝试这个查询

QUERY1：

select location,date_format(modefied_date,'%Y-%m-%d %H:%i %p') AS datetime from locatio_table where date(modefied_date) ='2017-12-26'

此查询显示空结果

query2：

select location,date_format(modefied_date,'%Y-%m-%d %H:%i %p') AS datetime from locatio_table

此查询显示位置＆＃39; null＆＃39; 结果

Answer 1

查询1：

mysql> select location,date_format(modefied_date,'%Y-%m-%d %H:%i %p') AS datetime from locatio_table where date(modefied_date) ='2017-12-26';
+----------+---------------------+
| location | datetime            |
+----------+---------------------+
| salem    | 2017-12-26 12:21 PM |
+----------+---------------------+
1 row in set (0.00 sec)

查询2：

mysql> select location,date_format(modefied_date,'%Y-%m-%d %H:%i %p') AS datetime from locatio_table;
+----------+---------------------+
| location | datetime            |
+----------+---------------------+
| salem    | 2017-12-26 12:21 PM |
+----------+---------------------+
1 row in set (0.00 sec)

您的查询正在按预期提供输出。没有结果为null / empty。