MySQL 如何将“ON 更新当前时间戳”添加到现有表列
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/9517630/
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
How to add "ON update current timestamp" to existing table column
提问by Rahul
i have column say ts_activity with datatype timestamp in MYSQL and default value to current timestamp. I want to add on update apply current time stamp to this column value.
我有列说 ts_activity 数据类型为 MYSQL 中的时间戳，默认值为当前时间戳。我想将更新应用当前时间戳添加到此列值。
I am not able to get alter query to do this. while create new table and its column i can add that, But not able to modify existing column by adding on update apply current timestamp.
我无法通过更改查询来执行此操作。在创建新表及其列时，我可以添加它，但无法通过添加更新应用当前时间戳来修改现有列。
Can some one tell me exact query to handle this. Can we alter this after creating table.
有人可以告诉我确切的查询来处理这个问题。我们可以在创建表后更改它吗？
Thanks
谢谢
回答by Ike Walker
Devart's suggestion will work, but I prefer to use MODIFY COLUMNinstead of CHANGE COLUMNif I'm not renaming the column.
Devart 的建议会起作用，但如果我不重命名列，我更喜欢使用MODIFY COLUMN而不是CHANGE COLUMN。
I also assume that your ts_activity column is not nullable since you have a default, so I am setting it to NOT NULL, but that's up to you.
我还假设您的 ts_activity 列不可为空，因为您有默认值，因此我将其设置为 NOT NULL，但这取决于您。
This is the statement I would use:
这是我将使用的语句：
ALTER TABLE your_table
MODIFY COLUMN ts_activity TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;
回答by Devart
Try this query -
试试这个查询 -
ALTER TABLE table_name
CHANGE COLUMN column_name column_name TIMESTAMP NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;
Note, in the table only one field can be with 'ON UPDATE CURRENT_TIMESTAMP' option.
注意，表中只有一个字段可以带有“ON UPDATE CURRENT_TIMESTAMP”选项。
