The difference between int (1) and int (10)

We know that mysql in int Occupy 4 Bytes , So for unsigned int, The maximum is 2^32-1 = 4294967295, nearly 40 Billion , Did you use it int(1), Can't you reach this maximum ？

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

id The field is unsigned int(1), Let me insert a maximum to see .

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

You can see the success , explain int Back number , No effect int Size supported by itself ,int(1)、int(2)…int(10) No difference .

commonly int Back number , coordination zerofill It works when used together . Let's take an example ：

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

mysql> INSERT INTO `user` (`id`) VALUES (1),(10),(100),(1000);
Query OK, 4 rows affected (0.00 sec)
Records: 4  Duplicates: 0  Warnings: 0

Insert separately 1、10、100、1000 4 Data , Then let's check ：

mysql> select * from user;
+------+
| id   |
+------+
| 0001 |
| 0010 |
| 0100 |
| 1000 |
+------+
4 rows in set (0.00 sec)

Through the data, we can find int(4) + zerofill Realized the deficiency 4 Place complement 0 The phenomenon of , only int(4) It's no use .