数据类型之【数值类型】的整数型smallint

1.1 smallint说明

id smallint(M) [UNSIGNED] [ZEROFILL]

字段名 字段类型(长度) [无符号] [前导填充]

unsigned：

01：smallint(M)后面加上unsigned,就是无符号(smallint的范围就是0~65535)

02：smallint(M)后面不加上unsigned,并且不加ZEROFILL参数，就是有符号(smallint的范围就是

-32768~32767)

zerofill：

01：进行前导零填充

02：smallint(M)加上zerofile后，同时也会把unsigned参数也带上(smallint范围0~65535)

1.2 smallint实践

1.2.1 环境准备

##创建chenliang库

mysql> create database if not exists chenliang;

Query OK, 1 row affected (0.03 sec)

mysql> show databases like "chenliang";

+----------------------+

| Database (chenliang) |

+----------------------+

| chenliang |

+----------------------+

1 row in set (0.03 sec)

##进入chenliang库

mysql> use chenliang;

Database changed

mysql> select database();

+------------+

| database() |

+------------+

| chenliang |

+------------+

1 row in set (0.01 sec)

1.2.2 加unsigned参数

##创建test1测试表(这里指定了UNSIGNED，也就是无符号)

mysql> CREATE TABLE IF NOT EXISTS test1(

->id smallint(5) UNSIGNED

->);

Query OK, 0 rows affected (0.03 sec)

^==test1表的id字段指定了unsigned参数，那么id字段的范围就是0~65535

mysql> desc test1;

+-------+----------------------+------+-----+---------+-------+

| Field | Type | Null | Key | Default | Extra |

+-------+----------------------+------+-----+---------+-------+

| id | smallint(5) unsigned | YES | | NULL | |

+-------+----------------------+------+-----+---------+-------+

1 row in set (0.00 sec)

**测试01：测试插入范围0~65535的整数以及超过65535的整数

mysql> insert into test1 values(0); #插入整数0,正确(没有超过范围0~65535)

Query OK, 1 row affected (0.03 sec)

mysql> insert into test1 values(65535); #插入整数65535,正确(没有超过范围0~65535)

Query OK, 1 row affected (0.03 sec)

mysql> insert into test1 values(65536); #插入整数65536,错误(超过范围0~65535)

ERROR 1264 (22003): Out of range value for column 'id' at row 1

mysql> select * from test1;

+-------+

| id |

+-------+

| 0 |

| 65535 |

+-------+

2 rows in set (0.00 sec)

**测试02：测试-1~-32768范围的负整数，以及小于-32768的负整数

mysql> insert into test1 values(-1);

ERROR 1264 (22003): Out of range value for column 'id' at row 1

^==插入负整数-1,报错(因为建表时,id字段加了unsigned参数,id字段的范围为0~65535)

mysql> INSERT INTO test1 values(-128);

ERROR 1264 (22003): Out of range value for column 'id' at row 1

^==插入负整数-128,报错(因为建表时,id字段加了unsigned参数,id字段的范围为0~65535)

mysql> insert into test1 values(-32769);

ERROR 1264 (22003): Out of range value for column 'id' at row 1

^==插入负整数-32769,报错(因为建表时,id字段加了unsigned参数,id字段的范围为0~65535)

mysql> select * from test1;

+-------+

| id |

+-------+

| 0 |

| 65535 |

+-------+

2 rows in set (0.01 sec)

1.2.3 加zerofill参数

##创建test2表，(这里指定了zerofill,也就是前导零填充)

mysql> create table if not exists test2(

-> id smallint(5) zerofill

-> );

Query OK, 0 rows affected (0.12 sec)

^==test2表的id字段指定了zerofill参数，它会把unsigned参数也带上，那么id字段的范

围就是0~65535

mysql> desc test2;

+-------+-------------------------------+------+-----+---------+-------+

| Field | Type | Null | Key | Default | Extra |

+-------+-------------------------------+------+-----+---------+-------+

| id | smallint(5) unsigned zerofill | YES | | NULL | |

+-------+-------------------------------+------+-----+---------+-------+

1 row in set (0.00 sec)

**测试01：测试插入范围0~65535的整数和超过65535的整数

mysql> insert into test2 values(0); #插入整数0，在0~65535范围内，正确

Query OK, 1 row affected (0.04 sec)

mysql> insert into test2 values(65535); #插入整数65535，在0~65535范围内，正确

Query OK, 1 row affected (0.05 sec)

mysql> insert into test2 values(65536); #插入整数65536，不在0~65535范围内，错误

ERROR 1264 (22003): Out of range value for column 'id' at row 1

mysql> select * from test2;

+-------+

| id |

+-------+

| 00000 |

| 65535 |

+-------+

2 rows in set (0.00 sec)

**测试02：测试-1~-32768范围的负整数，以及小于-32768的负整数

mysql> INSERT INTO test2 values(-1);

ERROR 1264 (22003): Out of range value for column 'id' at row 1

^==插入负整数-1，错误(因为在id字段加了zerofill参数，它会把unsigned也带上，所以

id字段的范围为0~65535)

mysql> INSERT INTO test2 values(-128);

ERROR 1264 (22003): Out of range value for column 'id' at row 1

^==插入负整数-128，错误(因为在id字段加了zerofill参数，它会把unsigned也带上，所

以id字段的范围为0~65535)

mysql> insert into test2 values(-32769);

ERROR 1264 (22003): Out of range value for column 'id' at row 1

^==插入负整数-32769，错误(因为在id字段加了zerofill参数，它会把unsigned也带上，

所以id字段的范围为0~65535,并且有符号的范围也只是-32768~32767)

mysql> select * from test2;

+-------+

| id |

+-------+

| 00000 |

| 65535 |

+-------+

2 rows in set (0.00 sec)

1.2.4 不加unsigned和zerofill参数

##创建test3表(不加unsigned和zerofill)

mysql> create table if not exists test3(

-> id smallint(5)

-> );

Query OK, 0 rows affected (0.08 sec)

^==test3表的id字段没指定unsigned和zerofill参数，那么id字段的范围就

是 -32768~32767

mysql> desc test3;

+-------+-------------+------+-----+---------+-------+

| Field | Type | Null | Key | Default | Extra |

+-------+-------------+------+-----+---------+-------+

| id | smallint(5) | YES | | NULL | |

+-------+-------------+------+-----+---------+-------+

1 row in set (0.01 sec)

**测试01：测试插入整数0~32767和超过32767的整数

mysql> insert into test3 values(0);

Query OK, 1 row affected (0.00 sec)

^==插入整数0，正确(在范围-32768~32767范围内)

mysql> insert into test3 values(32767);

Query OK, 1 row affected (0.04 sec)

^==插入整数32767，正确(在范围-32768~32767范围内)

mysql> insert into test3 values(32768);

ERROR 1264 (22003): Out of range value for column 'id' at row 1

^==插入整数32768，错误(不在范围-32768~32767范围内)

mysql> select * from test3;

+-------+

| id |

+-------+

| 0 |

| 32767 |

+-------+

2 rows in set (0.00 sec)

**测试02：测试插入负数-1~-32768和小于-32768的负数

mysql> INSERT INTO test3 values(-1);

Query OK, 1 row affected (0.10 sec)

^==插入负整数-1，正确(在范围-32768~32767范围内)

mysql> INSERT INTO test3 values(-128);

Query OK, 1 row affected (0.02 sec)

^==插入负整数-128，正确(在范围-32768~32767范围内)

mysql> insert into test3 values(-32769);

ERROR 1264 (22003): Out of range value for column 'id' at row 1

^==插入负整数-32769，错误(不在范围-32768~32767范围内)

mysql> select * from test3;

+-------+

| id |

+-------+

| 0 |

| 32767 |

| -1 |

| -128 |

+-------+

4 rows in set (0.00 sec)

1.3 smallint总结

格式：

id smallint(M) [UNSIGNED] [ZEROFILL]

字段名 字段类型(长度) [无符号] [前导填充]

unsigned：

01：smallint(M)后面加上unsigned后,就是无符号(smallint的范围就是0~65535)

02：smallint(M)后面不加上unsigned,并且不加zerofill参数,就是有符号(smallint的范围就是

-32768~32767)

zerofill：

01：进行前导零填充(插入数值1，表中显示的是00001，因为smallint的长度为5)

02：smallint(M)加上zerofile后，同时也会把unsigned参数也带上(smallint的范围为0~65535)