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 | +---------------------+-------------------+-------------------+----------+-----------+------------+----------+---------+
