mysql - 为什么 CAST() 函数返回错误的日期？

Question

我正在尝试从时间戳字段中获取日期部分。 我使用了这个 SQL 查询:

select timestamp, CAST(timestamp as date) as date from messages

我得到了以下结果:

--------------------------------------------
|        timestamp        |      date      |
--------------------------------------------
|   2016-05-15 10:22:54   |   2016-05-16   |
--------------------------------------------

如上所示，生成的日期字段返回错误的日期2016-05-16，而原始日期为2016-05-15。

我们如何解决这个问题？

Answer 1

这不是问题!!!它只设置了错误的时区。看样本

获取当前时区

SHOW GLOBAL VARIABLES LIKE 'time_zone'; -- systemwide setting
SHOW VARIABLES LIKE 'time_zone'; -- session setting

样本

MariaDB [mysql]> select t, CAST(t as date) FROM groupme LIMIT 1;
+---------------------+-----------------+
| t                   | CAST(t as date) |
+---------------------+-----------------+
| 2016-05-15 20:22:54 | 2016-05-15      |
+---------------------+-----------------+
1 row in set (0.00 sec)

MariaDB [mysql]> SET  time_zone ='-12:00';
Query OK, 0 rows affected (0.00 sec)

MariaDB [mysql]> select t, CAST(t as date) FROM groupme LIMIT 1;
+---------------------+-----------------+
| t                   | CAST(t as date) |
+---------------------+-----------------+
| 2016-05-14 20:22:54 | 2016-05-14      |
+---------------------+-----------------+
1 row in set (0.00 sec)

MariaDB [mysql]>