MySQL TIMESTAMP 默认为 NULL，而不是 CURRENT_TIMESTAMP
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/20520443/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
MySQL TIMESTAMP to default NULL, not CURRENT_TIMESTAMP
提问by natsuki_2002
Using MySQL, I'm trying to make a timestamp column from a date column and a time column. If the date or time column contains a NULL value, MySQL automatically sets the corresponding value in the TIMESTAMPcolumn to the CURRENT_TIMESTAMP.
使用 MySQL，我试图从日期列和时间列创建时间戳列。如果日期或时间列包含 NULL 值，MySQL 会自动将TIMESTAMP列中的相应值设置为CURRENT_TIMESTAMP.
Is there a way to make it default to a NULL, instead of the CURRENT_TIMESTAMP?
有没有办法让它默认为 a NULL，而不是CURRENT_TIMESTAMP？
Something like:
就像是：
ALTER TABLE customers ADD s_timestamp TIMESTAMP;
UPDATE customers
SET s_timestamp = timestamp(s_date,s_time) DEFAULT NULL;
回答by zessx
Use this query to add your column
使用此查询添加您的列
ALTER TABLE `customers`
ADD COLUMN `s_timestamp` TIMESTAMP NULL DEFAULT NULL;
And, if you want to get current timestamp on update only :
而且，如果您只想在更新时获取当前时间戳：
ALTER TABLE `customers`
ADD COLUMN `s_timestamp` TIMESTAMP NULL DEFAULT NULL ON UPDATE CURRENT_TIMESTAMP;
回答by niyou
I thought this should work:
我认为这应该有效：
ALTER TABLE customers ADD COLUMN s_timestamp TIMESTAMP DEFAULT NULL;
