I have table that doesn't need a specific field to be the primary key. I could add a auto-increment ID field, but it won't be used at all within database queries...
我有一个表不需要特定的字段作为主键。我可以添加一个自动增量ID字段,但在数据库查询中根本不会使用它...
Can I make a UNIQUE KEY to be primary too?
我可以制作一个独特的钥匙也是主要的吗?
the UNIQUE KEY consists of two fields paired together:
UNIQUE KEY由两个配对的字段组成:
a VARCHAR(64) NOT NULL,
b VARCHAR(64) NOT NULL,
UNIQUE KEY uk_ab(a,b)
3 个解决方案
#1
6
Sure (no need for UNIQUE KEY):
当然(不需要UNIQUE KEY):
PRIMARY KEY (a, b)
Have a look at the documentation:
看看文档:
A
PRIMARY KEYis a unique index where all key columns must be defined asNOT NULL. If they are not explicitly declared asNOT NULL, MySQL declares them so implicitly (and silently). A table can have only onePRIMARY KEY. The name of aPRIMARY KEYis alwaysPRIMARY, which thus cannot be used as the name for any other kind of index.PRIMARY KEY是一个唯一索引,其中所有键列必须定义为NOT NULL。如果它们没有显式声明为NOT NULL,那么MySQL会隐式地(并且默默地)声明它们。一个表只能有一个PRIMARY KEY。 PRIMARY KEY的名称始终为PRIMARY,因此不能用作任何其他类型索引的名称。
and
A
PRIMARY KEYcan be a multiple-column index. However, you cannot create a multiple-column index using thePRIMARY KEYkey attribute in a column specification. Doing so only marks that single column as primary. You must use a separatePRIMARY KEY(index_col_name, ...)clause.PRIMARY KEY可以是多列索引。但是,您无法使用列规范中的PRIMARY KEY键属性创建多列索引。这样做只会将单列标记为主列。您必须使用单独的PRIMARY KEY(index_col_name,...)子句。
#2
1
Not sure if this would work...
不确定这是否有效......
PRIMARY KEY uk_ab(a,b)
#3
1
If your table already has a unique constraint, then you need to add primary key (ALTER TABLE [table_name] ADD CONSTRAINT [constraint_name] PRIMARY KEY (a,b)), and drop the existing unique constraint. Otherwise, you will have 2 unique indexes on the same columns.
If you create a new table, use PRIMARY KEY(a,b) instead of UNIQUE(a,b) as proposed by others.
如果表已具有唯一约束,则需要添加主键(ALTER TABLE [table_name] ADD CONSTRAINT [constraint_name] PRIMARY KEY(a,b)),并删除现有唯一约束。否则,您将在同一列上拥有2个唯一索引。如果您创建一个新表,请使用PRIMARY KEY(a,b)而不是其他人提出的UNIQUE(a,b)。
#1
6
Sure (no need for UNIQUE KEY):
当然(不需要UNIQUE KEY):
PRIMARY KEY (a, b)
Have a look at the documentation:
看看文档:
A
PRIMARY KEYis a unique index where all key columns must be defined asNOT NULL. If they are not explicitly declared asNOT NULL, MySQL declares them so implicitly (and silently). A table can have only onePRIMARY KEY. The name of aPRIMARY KEYis alwaysPRIMARY, which thus cannot be used as the name for any other kind of index.PRIMARY KEY是一个唯一索引,其中所有键列必须定义为NOT NULL。如果它们没有显式声明为NOT NULL,那么MySQL会隐式地(并且默默地)声明它们。一个表只能有一个PRIMARY KEY。 PRIMARY KEY的名称始终为PRIMARY,因此不能用作任何其他类型索引的名称。
and
A
PRIMARY KEYcan be a multiple-column index. However, you cannot create a multiple-column index using thePRIMARY KEYkey attribute in a column specification. Doing so only marks that single column as primary. You must use a separatePRIMARY KEY(index_col_name, ...)clause.PRIMARY KEY可以是多列索引。但是,您无法使用列规范中的PRIMARY KEY键属性创建多列索引。这样做只会将单列标记为主列。您必须使用单独的PRIMARY KEY(index_col_name,...)子句。
#2
1
Not sure if this would work...
不确定这是否有效......
PRIMARY KEY uk_ab(a,b)
#3
1
If your table already has a unique constraint, then you need to add primary key (ALTER TABLE [table_name] ADD CONSTRAINT [constraint_name] PRIMARY KEY (a,b)), and drop the existing unique constraint. Otherwise, you will have 2 unique indexes on the same columns.
If you create a new table, use PRIMARY KEY(a,b) instead of UNIQUE(a,b) as proposed by others.
如果表已具有唯一约束,则需要添加主键(ALTER TABLE [table_name] ADD CONSTRAINT [constraint_name] PRIMARY KEY(a,b)),并删除现有唯一约束。否则,您将在同一列上拥有2个唯一索引。如果您创建一个新表,请使用PRIMARY KEY(a,b)而不是其他人提出的UNIQUE(a,b)。