Mysql：时区问题

Mysql：时区问题

1、时区配置

• Mysql默认使用系统的时区

mysql> show global variables like '%time%zone%';
+------------------+--------+
| Variable_name    | Value  |
+------------------+--------+
| system_time_zone |        |
| time_zone        | SYSTEM |	# 表明使用系统时间
+------------------+--------+
2 rows in set, 1 warning (0.17 sec)

mysql>

• 在Mysql配置文件中设置时区

修改完配置之后，需要重启MySQL服务，否则不生效。

[mysqld]

# 设置默认时区
# default-time-zone='+08:00'

修改之后在终端查看是否生效

mysql> show variables like '%time_zone%';
+------------------+--------+
| Variable_name    | Value  |
+------------------+--------+
| system_time_zone |        |
| time_zone        | +08:00 |
+------------------+--------+
2 rows in set, 1 warning (0.03 sec)

mysql>
# 设置新的时区
mysql>  SET TIME_ZONE = '-6:00';
Query OK, 0 rows affected (0.00 sec)
# 查看设置的时区是否生效
mysql> show variables like '%time_zone%';
+------------------+--------+
| Variable_name    | Value  |
+------------------+--------+
| system_time_zone |        |
| time_zone        | -06:00 |
+------------------+--------+
2 rows in set, 1 warning (0.00 sec)

mysql> 

2、时区影响了什么

2.1、now() curtime()系统函数的影响

mysql> select now(), curtime();
+---------------------+-----------+
| now()               | curtime() |
+---------------------+-----------+
| 2024-07-09 16:27:06 | 16:27:06  |
+---------------------+-----------+
1 row in set (0.02 sec)

mysql>
mysql>
mysql>  show variables like '%time_zone%';
+------------------+--------+
| Variable_name    | Value  |
+------------------+--------+
| system_time_zone |        |
| time_zone        | SYSTEM |
+------------------+--------+
2 rows in set, 1 warning (0.00 sec)

mysql>
mysql>
mysql> SET TIME_ZONE = '-6:00';
Query OK, 0 rows affected (0.00 sec)

mysql>  show variables like '%time_zone%';
+------------------+--------+
| Variable_name    | Value  |
+------------------+--------+
| system_time_zone |        |
| time_zone        | -06:00 |
+------------------+--------+
2 rows in set, 1 warning (0.00 sec)

# 修改时区之后，系统返回返回的值相应的也变化了
mysql> select now(), curtime();
+---------------------+-----------+
| now()               | curtime() |
+---------------------+-----------+
| 2024-07-09 02:28:03 | 02:28:03  |
+---------------------+-----------+
1 row in set (0.00 sec)

mysql>

2.2、timestamp 数据类型字段存储的数据受时区影响

• timestamp 数据类型会存储当时session的时区信息，读取时会根据当前 session 的时区进行转换；

• datetime 数据类型插入的是什么值，再读取就是什么值，不受时区影响。

  ​

  也可以理解为已经存储的数据是不会变的，只是 timestamp 类型数据在读取时会根据时区转换。

mysql> show global variables like '%time%zone%';
+------------------+--------+
| Variable_name    | Value  |
+------------------+--------+
| system_time_zone |        |
| time_zone        | SYSTEM |
+------------------+--------+
2 rows in set, 1 warning (0.17 sec)

mysql> create table datedemo
    -> (
    ->  mydatetime datetime,
    ->  mytimestamp timestamp
    -> );
Query OK, 0 rows affected (0.17 sec)

mysql>  select * from datedemo;
+---------------------+---------------------+
| mydatetime          | mytimestamp         |
+---------------------+---------------------+
| 2024-07-09 16:06:32 | 2024-07-09 16:06:32 |
| 2024-07-09 16:07:09 | NULL                |
| NULL                | NULL                |
+---------------------+---------------------+
3 rows in set (0.01 sec)

mysql>  SET TIME_ZONE = '-6:00';
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like '%time_zone%';
+------------------+--------+
| Variable_name    | Value  |
+------------------+--------+
| system_time_zone |        |
| time_zone        | -06:00 |
+------------------+--------+
2 rows in set, 1 warning (0.00 sec)

mysql> select * from datedemo;
+---------------------+---------------------+
| mydatetime          | mytimestamp         |
+---------------------+---------------------+
| 2024-07-09 16:06:32 | 2024-07-09 02:06:32 |# mytimestamp字段显示的值发生了转换
| 2024-07-09 16:07:09 | NULL                |
| NULL                | NULL                |
+---------------------+---------------------+
3 rows in set (0.00 sec)

mysql>