我可以在PostgreSQL表创建后添加UNIQUE约束吗？ [英] Can I add a UNIQUE constraint to a PostgreSQL table, after it's already created?

问题描述

我有下表：

 tickername | tickerbbname  | tickertype
------------+---------------+------------
 USDZAR     | USDZAR Curncy | C
 EURCZK     | EURCZK Curncy | C
 EURPLN     | EURPLN Curncy | C
 USDBRL     | USDBRL Curncy | C
 USDTRY     | USDTRY Curncy | C
 EURHUF     | EURHUF Curncy | C
 USDRUB     | USDRUB Curncy | C

我不希望任何给定<$ c $的列数超过一列c> tickername / tickerbbname 对。我已经创建了表并且其中包含大量数据（我已经确保它符合唯一标准）。然而，随着它变得越来越大，错误的空间也在蔓延。

I don't want there to ever be more than one column for any given tickername/tickerbbname pair. I've already created the table and have lots of data in it (which I have already ensured meets the unique criteria). As it gets larger, though, room for error creeps in.

有没有办法添加 UNIQUE 约束此时？

Is there any way to add a UNIQUE constraint at this point?

推荐答案

psql 的内联帮助：

\h ALTER TABLE

还有 postgres docs （一个优秀的资源，加上易于阅读）。

Also documented in the postgres docs (an excellent resource, plus easy to read, too).

ALTER TABLE tablename ADD CONSTRAINT constraintname UNIQUE (columns);

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