本文介绍了ALTER TABLE添加一个复合主键的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我有一个名为provider的表.我有三列分别称为person，place，thing.可以有重复的人，重复的地方和重复的事物，但是永远不可能有重复的人与事物的组合.
I have a table called provider. I have three columns called person, place, thing. There can be duplicate persons, duplicate places, and duplicate things, but there can never be a dupicate person-place-thing combination.
我如何通过以下三列在ALTER TABLE中为该表添加一个复合主键?
How would I ALTER TABLE to add a composite primary key for this table in MySQL with the these three columns?
推荐答案
ALTER TABLE provider ADD PRIMARY KEY(person,place,thing);
如果主键已经存在，那么您要这样做
If a primary key already exists then you want to do this
ALTER TABLE provider DROP PRIMARY KEY, ADD PRIMARY KEY(person, place, thing);
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