MySQL 字段类型 (int) (mediumint) (smallint) (tinyint)

mysql> desc test;
+-------+-----------------------+------+-----+---------+----------------+
| Field | Type                  | Null | Key | Default | Extra          |
+-------+-----------------------+------+-----+---------+----------------+
| id    | int(10)               | NO   | PRI | NULL    | auto_increment |
| one   | int(11)               | YES  |     | NULL    |                |
| two   | int(10) unsigned      | YES  |     | NULL    |                |
| three | mediumint(9)          | YES  |     | NULL    |                |
| four  | mediumint(8) unsigned | YES  |     | NULL    |                |
| five  | smallint(6)           | YES  |     | NULL    |                |
| six   | smallint(5) unsigned  | YES  |     | NULL    |                |
| seven | tinyint(4)            | YES  |     | NULL    |                |
| eight | tinyint(3) unsigned   | YES  |     | NULL    |                |
+-------+-----------------------+------+-----+---------+----------------+
9 rows in set (0.01 sec)

int

mysql> insert into test (one) values (2147483648);
ERROR 1264 (22003): Out of range value for column 'one' at row 1
mysql> insert into test (one) values (2147483647);
Query OK, 1 row affected (0.00 sec)

mysql> insert into test (one) values (-2147483648);
Query OK, 1 row affected (0.00 sec)

mysql> insert into test (one) values (-2147483649);
ERROR 1264 (22003): Out of range value for column 'one' at row 1
mysql> insert into test (two) values (4294967296);
ERROR 1264 (22003): Out of range value for column 'two' at row 1
mysql> insert into test (two) values (4294967295);
Query OK, 1 row affected (0.00 sec)
mysql> select one, two from test;
+-------------+------------+
| one         | two        |
+-------------+------------+
|  2147483647 |       NULL |
| -2147483648 |       NULL |
|        NULL | 4294967295 |
+-------------+------------+
3 rows in set (0.00 sec)

mediumint

mysql> insert into test (three) values (8388608);
ERROR 1264 (22003): Out of range value for column 'three' at row 1
mysql> insert into test (three) values (8388607);
Query OK, 1 row affected (0.00 sec)

mysql> insert into test (three) values (-8388608);
Query OK, 1 row affected (0.00 sec)

mysql> insert into test (three) values (-8388609);
ERROR 1264 (22003): Out of range value for column 'three' at row 1
mysql> insert into test (four) values (16777216);
ERROR 1264 (22003): Out of range value for column 'four' at row 1
mysql> insert into test (four) values (16777215);
Query OK, 1 row affected (0.00 sec)

mysql> select three, four from test;
+----------+----------+
| three    | four     |
+----------+----------+
|  8388607 |     NULL |
| -8388608 |     NULL |
|     NULL | 16777215 |
+----------+----------+
6 rows in set (0.00 sec)

smallint

mysql> insert into test (five) values (32767);
Query OK, 1 row affected (0.00 sec)

mysql> insert into test (five) values (-32768);
Query OK, 1 row affected (0.00 sec)

mysql> insert into test (five) values (-32769);
ERROR 1264 (22003): Out of range value for column 'five' at row 1
mysql> insert into test (six) values (65536);
ERROR 1264 (22003): Out of range value for column 'six' at row 1
mysql> insert into test (six) values (65535);
Query OK, 1 row affected (0.00 sec)

mysql> select five, six from test;
+--------+-------+
| five   | six   |
+--------+-------+
|  32767 |  NULL |
| -32768 |  NULL |
|   NULL | 65535 |
+--------+-------+
9 rows in set (0.00 sec)

tinyint

mysql> insert into test (seven) values (128);
ERROR 1264 (22003): Out of range value for column 'seven' at row 1
mysql> insert into test (seven) values (127);
Query OK, 1 row affected (0.00 sec)

mysql> insert into test (seven) values (-128);
Query OK, 1 row affected (0.00 sec)

mysql> insert into test (seven) values (-129);
ERROR 1264 (22003): Out of range value for column 'seven' at row 1
mysql> insert into test (eight) values (256);
ERROR 1264 (22003): Out of range value for column 'eight' at row 1
mysql> insert into test (eight) values (255);
Query OK, 1 row affected (0.00 sec)

mysql> select seven, eight from test;
+-------+-------+
| seven | eight |
+-------+-------+
|   127 |  NULL |
|  -128 |  NULL |
|  NULL |   255 |
+-------+-------+
12 rows in set (0.00 sec)

总结如下：

int 四个字节 无符号 0 ~ 2^32 -1

mediumint 三个字节 无符号 0 ~ 2^24 -1

smallint 二个字节 无符号 0 ~ 2^16 -1

tinyint 一个字节 无符号 0 ~ 2^8 -1

tinyint(1) 的范围依然是0~255

mysql> desc one;
+-------+---------------------+------+-----+---------+-------+
| Field | Type                | Null | Key | Default | Extra |
+-------+---------------------+------+-----+---------+-------+
| num   | tinyint(1) unsigned | YES  |     | NULL    |       |
+-------+---------------------+------+-----+---------+-------+
1 row in set (0.00 sec)

mysql> insert into one (num) values (0);
Query OK, 1 row affected (0.00 sec)

mysql> insert into one (num) values (255);
Query OK, 1 row affected (0.00 sec)

mysql> insert into one (num) values (256);
ERROR 1264 (22003): Out of range value for column 'num' at row 1