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>
