MySQL int 类型不是最多只能到 4,294,967,295 么，怎么会有 int(11)？

Question

MySQL int 类型不是最多只能到 4,294,967,295 么，怎么新建表的时候，默认不写 int 后面的数字（即不这样写int(5)），建好表之后会是 int(11)

Answer 1

The following numbers only affect the number of digits displayed by default

http://www.ccvita.com/175.html

Answer 2

举个例子最明白，类似于位数不足以0补全。
e.g.

mysql> create table joke (a int(11));
Query OK, 0 rows affected (0.01 sec)

mysql> insert into joke values(100);
Query OK, 1 row affected (0.00 sec)

mysql> select * from joke;
+------+
| a |
+------+
| 100 |
+------+
1 row in set (0.00 sec)

mysql> alter table joke change a a int(11) zerofill;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0

mysql> select * from joke;
+-------------+
| a |
+-------------+
| 00000000100 |
+-------------+
1 row in set (0.00 sec)

Answer 3

int(11) here does not mean the maximum number of digits represented, but the number of digits displayed. For example, 123 will be displayed as 00000000123

in int(11)

Answer 4

You don’t need to specify the length of int when creating a table. What is displayed in this () is the width displayed externally. Int is a fixed-length data type. So the storage size is determined. It will not change because of ().

Answer 5

If it is a signed integer, there will be an extra negative sign

Answer 6

Is it okay?