日期从ActiveRecord恢复为MySQL的2000-01-01 [英] Date reverts to 2000-01-01 from ActiveRecord to MySQL
问题描述
我正在尝试在MySQL表中节省时间。但是，日期恢复为2000年1月1日。
I am trying to save a time in a MySQL table. However, the date reverts to 2000-01-01.
1.9.2p320 :036 > vv = Visitor.new
=> #<Visitor id: nil, ip_address: nil, num_day_visits: nil, last_visit: nil>
1.9.2p320 :037 > vv.last_visit = Time.now; vv.ip_address = "3.3.3.3"
=> "3.3.3.3"
1.9.2p320 :038 > vv.num_day_visits = 1
=> 1
1.9.2p320 :039 > vv
=> #<Visitor id: nil, ip_address: "3.3.3.3", num_day_visits: 1, last_visit: "2012-10-11 01:31:04">
1.9.2p320 :040 > vv.save
SQL (0.2ms) BEGIN
SQL (0.7ms) INSERT INTO `visitors` (`ip_address`, `last_visit`, `num_day_visits`) VALUES (?, ?, ?) [["ip_address", "3.3.3.3"], ["last_visit", 2012-10-11 01:31:04 -0400], ["num_day_visits", 1]]
(0.5ms) COMMIT
=> true
1.9.2p320 :042 > vv
=> #<Visitor id: 1199, ip_address: "3.3.3.3", num_day_visits: 1, last_visit: "2012-10-11 01:31:04">
1.9.2p320 :043 > Visitor.find(:all,:conditions=>{:ip_address => "3.3.3.3"})
Visitor Load (1.4ms) SELECT `visitors`.* FROM `visitors` WHERE `visitors`.`ip_address` = '3.3.3.3'
=> [#<Visitor id: 1199, ip_address: "3.3.3.3", num_day_visits: 1, last_visit: "2000-01-01 05:31:04">]
因此，当我检索记录时，日期为2000-01-01。
So when I retrieve the record, the date is 2000-01-01.
表在MySQL中：
mysql> describe visitors ;
+----------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| ip_address | varchar(255) | NO | | NULL | |
| num_day_visits | int(11) | NO | | NULL | |
| last_visit | time | NO | | NULL | |
+----------------+--------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)
更新：我创建了一个玩具桌，用于围绕时间到日期时间进行转换。这就是发生的情况：
Update: I created a toy table to play around the conversion from time to datetime. This is what happens:
mysql> select * from example ;
+----+----------+
| id | mytime |
+----+----------+
| 1 | 11:13:00 |
+----+----------+
1 row in set (0.00 sec)
mysql> alter table example change mytime mytime datetime;
Query OK, 1 row affected, 1 warning (0.02 sec)
Records: 1 Duplicates: 0 Warnings: 1
mysql> select * from example ;
+----+---------------------+
| id | mytime |
+----+---------------------+
| 1 | 0000-00-00 00:00:00 |
+----+---------------------+
1 row in set (0.00 sec)
因此这破坏了价值。我试图通过更改表时间并使用新行来返回。重新开始：
So that destroys the value. I tried to go back by altering the table to time, and using a new row. Starting over:
mysql> select * from example ;
+----+----------+
| id | mytime |
+----+----------+
| 2 | 11:13:00 |
+----+----------+
1 row in set (0.00 sec)
mysql> ALTER TABLE example CHANGE mytime mytime DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP();
ERROR 1067 (42000): Invalid default value for 'mytime'
mysql> ALTER TABLE example CHANGE mytime mytime DATETIME NOT NULL DEFAULT CURRENT_DATE();
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CURRENT_DATE()' at line 1
$ b $中，查看与您的MySQL服务器版本相对应的手册以获取在'CURRENT_DATE（）'附近使用的正确语法。 b
显然，这很难。
推荐答案
这是因为您的 last_visit 列是 time 而不是 datetime 类型。最初，我假设mysql只使用 01-01-2000 作为某种默认日期来内部表示时间字段，但是看来01-01-2000是这样做的Rails而不是mysql。查看表示没有日期的时间在红宝石中
This is because your last_visit column is of the time and not datetime type. Initially I assumed that mysql just uses 01-01-2000 as some sort of default date for representing time fields internally, however it appears that 01-01-2000 is the doing of rails and not mysql. Look at Represent a time with no date in ruby
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