Oracle 数据库，将唯一索引转换为非唯一索引
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Oracle database, converting unique index to non-unique one
提问by Haozhun
I understand I can't do this straightforward from studying similar questions on stackoverflow and other sites.
我知道我无法通过研究 stackoverflow 和其他网站上的类似问题直接做到这一点。
However, I need to do this and I'm willing to go with workarounds.
但是，我需要这样做并且我愿意采用变通方法。
I tried to create a non-unique index with onlineand parallel, and then drop the old unique index. However, it fails saying ORA-01408: such column list already indexed.
我尝试使用onlineand创建非唯一索引parallel，然后删除旧的唯一索引。但是，它没有说ORA-01408: such column list already indexed。
How to convert an unique index to a non-unique one?
如何将唯一索引转换为非唯一索引？
回答by Jeffrey Kemp
If you don't want to drop the old index before creating the new one, you can cheat a bit by creating the new index with an additional useless column, e.g.:
如果您不想在创建新索引之前删除旧索引，您可以通过使用额外的无用列创建新索引来作弊，例如：
Assuming a table with the following configuration:
假设一个表具有以下配置：
create table mytable (id number);
create unique index myunique on mytable (id);
To convert the index to non unique:
要将索引转换为非唯一：
create index temp on mytable (id, 1);
drop index myunique;
create index mynonunique on mytable (id);
drop index temp;
In practice I'm not sure how necessary this is - generally I'd just drop and recreate the index in some low-activity period, preferably take the application down.
在实践中，我不确定这有多必要 - 通常我只会在某个低活动期删除并重新创建索引，最好关闭应用程序。
