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This article will explain in detail the method of deleting the primary key in mysql. The editor thinks it is very practical, so I share it for you as a reference. I hope you can get something after reading this article.

First, let's look at the syntax for deleting a primary key:

ALTER TABLE TABLE_NAME DROP PRIMARY KEY

There are two situations to consider when deleting a primary key in MySQL:

1. The primary key column does not have any constraints and can be deleted directly.

Example:

Mysql > create table test1_3 (- > id int not null primary key,-> name char (10)->); Query OK, 0 rows affected (0.01 sec)

We can use drop directly to delete the primary key

Mysql > alter table test1_3 drop primary key;Query OK, 0 rows affected (0.02 sec) Records: 0 Duplicates: 0 Warnings: 0

2. If it is the primary key of self-increment (AUTO_INCREMENT attribute)

Example:

Mysql > create table test1_2 (- > id int not null auto_increment,-> name char (10),-> primary key (id)->); Query OK, 0 rows affected (0.00 sec) mysql > desc test1_2 +-+ | Field | Type | Null | Key | Default | Extra | +-+ -+ | id | int (11) | NO | PRI | NULL | auto_increment | | name | char (10) | YES | | NULL | | +-+-+ 2 rows in set (0.00 sec)

If you delete it directly, an error will be reported.

Mysql > alter table test1_2 drop primary key

Output:

ERROR 1075 (42000): Incorrect table definition; there can be only one auto column and it must be defined as a key # this means that this column is auto-growing and cannot be deleted directly

The property of the column also has an AUTO_INCREMENT, so the auto-grow attribute of this column must be removed before the primary key can be deleted.

Mysql > alter table test1_2 modify id int;Query OK, 0 rows affected (0.03 sec) Records: 0 Duplicates: 0 Warnings: 0mysql > alter table test1_2 drop primary key;Query OK, 0 rows affected (0.02 sec) Records: 0 Duplicates: 0 Warnings: 0 about the method of deleting the primary key by mysql, that's all. I hope the above content can be helpful to everyone and learn more knowledge. If you think the article is good, you can share it for more people to see.

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