mysql删除主键索引 mysql如何删除主键

要删除主键，请首先使用ALTER更改表。这样，使用DROP删除键，如下所示

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)
-> );
这是检查表说明的查询-mysql> desc DemoTable;+-------------+-------------+------+-----+---------+-------+
| 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;
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)