ALTER TABLE 添加复合主键
我有一个名为 provider
的表.我有三列名为person
、place
、thing
.可以有重复的人、重复的地点和重复的事物,但永远不可能有重复的人地物组合.
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.
如何使用这三列在 MySQL 中为该表添加复合主键?
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,那么你想这样做
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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