MySQL数据库：数据类型-整数
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数据类型-整数
| 字段类型 | 名称 | 字节数 | 表示范围 |
|---|---|---|---|
| tinyint | 迷你整型 | 1个字节=8位 | 0-255 |
| smallint | 小整型 | 2个字节 | 0-65535 |
| mediumint | 中整型 | 3个字节 | |
| int | 整型（标准整型） | 4个字节 | |
| bigint | 大整型 | 8个字节 |
通常使用较多的是int和tinyint
示例
create table my_int(
tiny_int tinyint,
small_int smallint,
medium_int mediumint,
int_ int,
big_int bigint
);
-- 插入正确的值
insert into my_int
(tiny_int, small_int, medium_int, int_, big_int)
values
(10, 10000, 100000, 10000000, 1000000);
mysql> select * from my_int;
+----------+-----------+------------+----------+---------+
| tiny_int | small_int | medium_int | int_ | big_int |
+----------+-----------+------------+----------+---------+
| 10 | 10000 | 100000 | 10000000 | 1000000 |
+----------+-----------+------------+----------+---------+
-- 插入一个超出范围的值
insert into my_int
(tiny_int, small_int, medium_int, int_, big_int)
values
(255, 255, 255, 255, 255);
ERROR 1264 (22003): Out of range value for column tiny_int at row 1
-- 原因是tinyint实际取值范围：-128~127，包含了负数
insert into my_int
(tiny_int, small_int, medium_int, int_, big_int)
values
(-128, 255, 255, 255, 255);
select * from my_int;
+----------+-----------+------------+----------+---------+
| tiny_int | small_int | medium_int | int_ | big_int |
+----------+-----------+------------+----------+---------+
| 10 | 10000 | 100000 | 10000000 | 1000000 |
| -128 | 255 | 255 | 255 | 255 |
+----------+-----------+------------+----------+---------+无符号标识（unsigned）
只要正数(0-255)
alter table my_int add unsigned_tiny_int tinyint unsigned first;
-- 插入255
insert into my_int
(unsigned_tiny_int, tiny_int, small_int, medium_int, int_, big_int)
values
(255, 127, 255, 255, 255, 255);
mysql> select * from my_int;
+-------------------+----------+-----------+------------+----------+---------+
| unsigned_tiny_int | tiny_int | small_int | medium_int | int_ | big_int |
+-------------------+----------+-----------+------------+----------+---------+
| NULL | 10 | 10000 | 100000 | 10000000 | 1000000 |
| NULL | -128 | 255 | 255 | 255 | 255 |
| 255 | 127 | 255 | 255 | 255 | 255 |
+-------------------+----------+-----------+------------+----------+---------+
mysql> desc my_int;
+-------------------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------------+---------------------+------+-----+---------+-------+
| unsigned_tiny_int | tinyint(3) unsigned | YES | | NULL | |
| tiny_int | tinyint(4) | YES | | NULL | |
| small_int | smallint(6) | YES | | NULL | |
| medium_int | mediumint(9) | YES | | NULL | |
| int_ | int(11) | YES | | NULL | |
| big_int | bigint(20) | YES | | NULL | |
+-------------------+---------------------+------+-----+---------+-------+显示长度zerofill
整型数据在显示的时候，最多可以显示的位数
- tinyint(3) 表示最长显示3位，unsigned是正数，0-255不会超过3个长度
- tinyint(4) 表示最长可以显示4位 -128~127
显示长度，只是代表了数据是否可以达到指定的长度，但是不会自动满足到指定长度，如果想要数据显示的时候，保持最高位（显示长度），需要增加zerofill属性
zerofill：从左侧开始填充0到指定位数，自动设置为unsigned
示例
alter table my_int add zerofill_tiny_int tinyint zerofill first;
desc my_int;
+-------------------+------------------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------------+------------------------------+------+-----+---------+-------+
| zerofill_tiny_int | tinyint(3) unsigned zerofill | YES | | NULL | |
| unsigned_tiny_int | tinyint(3) unsigned | YES | | NULL | |
| tiny_int | tinyint(4) | YES | | NULL | |
| small_int | smallint(6) | YES | | NULL | |
| medium_int | mediumint(9) | YES | | NULL | |
| int_ | int(11) | YES | | NULL | |
| big_int | bigint(20) | YES | | NULL | |
+-------------------+------------------------------+------+-----+---------+-------+
-- 插入数据
insert into my_int
(zerofill_tiny_int, unsigned_tiny_int, tiny_int, small_int, medium_int, int_, big_int)
values
(1, 1, 1, 1, 1, 1, 1);
select * from my_int;
+-------------------+-------------------+----------+-----------+------------+----------+---------+
| zerofill_tiny_int | unsigned_tiny_int | tiny_int | small_int | medium_int | int_ | big_int |
+-------------------+-------------------+----------+-----------+------------+----------+---------+
| NULL | NULL | 10 | 10000 | 100000 | 10000000 | 1000000 |
| NULL | NULL | -128 | 255 | 255 | 255 | 255 |
| NULL | 255 | 127 | 255 | 255 | 255 | 255 |
| 001 | 1 | 1 | 1 | 1 | 1 | 1 |
+-------------------+-------------------+----------+-----------+------------+----------+---------+自定义显示长度，不会改变字段所能表示的数据长度，超出长度不受影响，长度不足会补0
示例
alter table my_int add zerofill_tiny_int_2 tinyint(2) zerofill first;
desc my_int;
+---------------------+------------------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------------------+------------------------------+------+-----+---------+-------+
| zerofill_tiny_int_2 | tinyint(2) unsigned zerofill | YES | | NULL | |
| zerofill_tiny_int | tinyint(3) unsigned zerofill | YES | | NULL | |
| unsigned_tiny_int | tinyint(3) unsigned | YES | | NULL | |
| tiny_int | tinyint(4) | YES | | NULL | |
| small_int | smallint(6) | YES | | NULL | |
| medium_int | mediumint(9) | YES | | NULL | |
| int_ | int(11) | YES | | NULL | |
| big_int | bigint(20) | YES | | NULL | |
+---------------------+------------------------------+------+-----+---------+-------+
insert into my_int
(zerofill_tiny_int_2, zerofill_tiny_int, unsigned_tiny_int, tiny_int, small_int, medium_int, int_, big_int)
values
(100, 100, 100, 100, 100, 100, 100, 100),
(1, 1, 1, 1, 1, 1, 1, 1);
select * from my_int;
+---------------------+-------------------+-------------------+----------+-----------+------------+----------+---------+
| zerofill_tiny_int_2 | zerofill_tiny_int | unsigned_tiny_int | tiny_int | small_int | medium_int | int_ | big_int |
+---------------------+-------------------+-------------------+----------+-----------+------------+----------+---------+
| NULL | NULL | NULL | 10 | 10000 | 100000 | 10000000 | 1000000 |
| NULL | NULL | NULL | -128 | 255 | 255 | 255 | 255 |
| NULL | NULL | 255 | 127 | 255 | 255 | 255 | 255 |
| NULL | 001 | 1 | 1 | 1 | 1 | 1 | 1 |
| 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
| 01 | 001 | 1 | 1 | 1 | 1 | 1 | 1 |
+---------------------+-------------------+-------------------+----------+-----------+------------+----------+---------+
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