MySQL 添加以当前时间为默认值的新列
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Adding a new column with the current time as a default value
提问by RedPe4rl
I am looking for the syntax to add a column to a MySQL table with the current time as a default value.
我正在寻找将列添加到 MySQL 表的语法，并将当前时间作为默认值。
回答by Roman Marusyk
IMPORTANT EDIT:It is now possible to achieve this with DATETIMEfields since MySQL 5.6.5, take a look at the other postbelow...
重要编辑：现在可以使用MySQL 5.6.5DATETIME以来的字段来实现这一点，看看下面的另一篇文章......
It is now possible to achieve this with DATETIMEfields since MySQL 5.6.5
But you can do it with TIMESTAMP:
DATETIME从 MySQL 5.6.5 开始，现在可以使用字段来实现这一点，
但您可以使用TIMESTAMP：
create table test (str varchar(32), ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP)
回答by Zafar Malik
Even so many persons have provided solution but this is just to add more information-
即使有这么多人提供了解决方案，但这只是为了添加更多信息-
If you just want to insert current timestamp at the time of row insertion-
如果您只想在行插入时插入当前时间戳 -
ALTER TABLE mytable ADD mytimestampcol TIMESTAMP DEFAULT CURRENT_TIMESTAMP;
If you also want that this column should update if any update this row then use this-
如果您还希望此列在更新此行时更新，则使用此 -
ALTER TABLE mytable ADD mytimestampcol TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;
回答by Mureinik
You can specify a defaultclause:
您可以指定一个default子句：
ALTER TABLE mytable ADD COLUMN (mytimestamp TIMESTAMP DEFAULT CURRENT_TIMESTAMP);
回答by Venkatesh Panabaka
I think these sql will useful to you.
我认为这些 sql 对你有用。
create table test (column_name varchar(32), time_column TIMESTAMP DEFAULT CURRENT_TIMESTAMP);
mysql> insert into test (column_name) values ("demo");
Query OK, 1 row affected (0.00 sec)
mysql> select column_name as name, time_column as ts from test;
+------+---------------------+
| name | ts |
+------+---------------------+
| demo | 2014-07-31 15:42:52 |
+------+---------------------+
1 row in set (0.00 sec)
1 行（0.00 秒）
Thank you.
谢谢你。
回答by Manish Sapkal
create table test (col1 varchar(10), lastaccessdate TIMESTAMP(6) DEFAULT CURRENT_TIMESTAMP(6) ON UPDATE CURRENT_TIMESTAMP(6));
this will update time with fractional seconds in time, and also update when record is last inserted or updated.
这将更新时间以秒为单位，并在上次插入或更新记录时更新。
