Reset Primary Key in MySQL

To reset primary key, at first use TRUNCATE table, then use ALTER TABLE. Let us first create a table −

mysql> create table DemoTable1929
   (
   UserId int NOT NULL AUTO_INCREMENT,
   PRIMARY KEY(UserId)
   );
Query OK, 0 rows affected (0.00 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable1929 values();
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1929 values();
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1929 values();
Query OK, 1 row affected (0.00 sec)

Display all records from the table using select statement −

mysql> select * from DemoTable1929;

This will produce the following output −

+--------+
| UserId |
+--------+
|      1 |
|      2 |
|      3 |
+--------+
3 rows in set (0.00 sec)

Here is the query to reset primary key −

mysql> truncate table DemoTable1929;
Query OK, 0 rows affected (0.00 sec)
mysql> alter table DemoTable1929 auto_increment=1;
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

Now you can insert record, it will reset the primary key value from 1 −

mysql> insert into DemoTable1929 values();
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1929 values();
Query OK, 1 row affected (0.00 sec)

Display all records from table using select statement −

mysql> select * from DemoTable1929;

This will produce the following output −

+--------+
| UserId |
+--------+
|      1 |
|      2 |
+--------+
2 rows in set (0.00 sec)