MySQL 如何在MySQL中删除主键？

要删除主键，首先使用ALTER来修改表。然后使用DROP删除主键，如下所示

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语法

alter table yourTableName drop primary key;

让我们首先创建一个表 –

mysql> create table DemoTable
   -> (
   -> StudentId int NOT NULL,
   -> StudentName varchar(20),
   -> StudentAge int,
   -> primary key(StudentId)
   -> );
Query OK, 0 rows affected (0.48 sec)

以下是查询表描述的查询 –

mysql> desc DemoTable;

这将产生以下输出 –

+-------------+-------------+------+-----+---------+-------+
| Field       | Type        | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+-------+
| StudentId   | int(11)     | NO   | PRI | NULL    |       |
| StudentName | varchar(20) | YES  |     | NULL    |       |
| StudentAge  | int(11)     | YES  |     | NULL    |       |
+-------------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

以下是在MySQL中删除主键的查询 –

mysql> alter table DemoTable drop primary key;
Query OK, 0 rows affected (1.70 sec)
Records: 0 Duplicates: 0 Warnings: 0

让我们再次检查表描述 –

mysql> desc DemoTable;

这将产生以下输出 –

+-------------+-------------+------+-----+---------+-------+
| Field       | Type        | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+-------+
| StudentId   | int(11)     | NO   |     | NULL    |       |
| StudentName | varchar(20) | YES  |     | NULL    |       |
| StudentAge  | int(11)     | YES  |     | NULL    |       |
+-------------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)