Understanding MySQL INT Display Width and ZEROFILL

When adding a user_id column, the author initially used int(1) and was told the size might be insufficient; however, the display width in MySQL does not affect the actual range of the integer type.

In MySQL an INT occupies 4 bytes, so an unsigned INT can store values up to 2^32‑1 (= 4294967295). The author created a table with int(1) unsigned and successfully inserted the maximum value, proving that int(1) , int(2) … int(10) all have the same range.

CREATE TABLE `user` (
  `id` int(1) unsigned NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4;

mysql> INSERT INTO `user` (`id`) VALUES (4294967295);
Query OK, 1 row affected (0.00 sec)

The numeric argument only influences the display width when used together with the ZEROFILL attribute. The author then created a table with int(4) unsigned ZEROFILL , inserted several values, and queried the table to show the padded output.

CREATE TABLE `user` (
  `id` int(4) unsigned ZEROFILL NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4;

INSERT INTO `user` (`id`) VALUES (1),(10),(100),(1000);
Query OK, 4 rows affected (0.00 sec)

SELECT * FROM user;
+------+ 
| id   |
+------+ 
| 0001 |
| 0010 |
| 0100 |
| 1000 |
+------+ 
4 rows in set (0.00 sec)

This demonstrates that ZEROFILL pads numbers to the specified display width, while the width itself does not constrain the stored value; the underlying storage remains the same.

In summary, the number in INT(n) does not represent the column’s capacity; only when combined with ZEROFILL does the display width affect how numbers are presented, useful for fixed‑length identifiers.