SQL Oracle 将日期列添加到现有表（默认为仅 sysdate 新行）
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Oracle Add Date Column to Existing Table (default to sysdate new rows only)
提问by NealWalters
Is there a way to add column DATE_CREATED such as only new rows will pickup the default sysdate? When I ran the ALTER below, all priors rows got the DATE_CREATED set to the run-time of the ALTER script; I would prefer them to remain null.
有没有办法添加列 DATE_CREATED 例如只有新行会选择默认的系统日期？当我运行下面的 ALTER 时，所有先验行都将 DATE_CREATED 设置为 ALTER 脚本的运行时；我希望它们保持为空。
alter table abc.mytable
add
(DATE_CREATED date default sysdate null
);
回答by a_horse_with_no_name
You need to first add the column without a default:
您需要先添加没有默认值的列：
alter table mytable add date_created date default null;
and then add define the default value:
然后添加定义默认值：
alter table mytable modify date_created default sysdate;
