Can we remove a primary key from MySQL table?

Yes, we can remove a primary key using the DROP in MySQL. Following is the syntax −

alter table yourTableName drop primary key;

Let us first create a table −

mysql> create table DemoTable
   (
      UserId int NOT NULL PRIMARY KEY
   );
Query OK, 0 rows affected (0.58 sec)

Following is the query to check the description of table −

mysql> desc DemoTable;

This will produce the following output displaying the Primary Key −

+--------+---------+------+-----+---------+-------+
| Field  | Type    | Null | Key | Default | Extra |
+--------+---------+------+-----+---------+-------+
| UserId | int(11) | NO   | PRI | NULL    |       |
+--------+---------+------+-----+---------+-------+
1 row in set (0.01 sec)

Following is the query to remove primary key from table −

mysql> alter table DemoTable drop primary key;
Query OK, 0 rows affected (1.51 sec)
Records: 0 Duplicates: 0 Warnings: 0

Let us check the description of the table once again −

mysql> desc DemoTable;

This will produce the following output. Now the primary key isn’t visible −

+--------+---------+------+-----+---------+-------+
| Field  | Type    | Null | Key | Default | Extra |
+--------+---------+------+-----+---------+-------+
| UserId | int(11) | NO   |     | NULL    |       |
+--------+---------+------+-----+---------+-------+
1 row in set (0.01 sec)