mysql 中int(1)和tinyint(1)中的1只是指定显示长度,并不表示存储长度,只有字段指定zerofill是有用 如int(3),如果实际值是2,如果列指定了zerofill,查询结果就是002,左边用0来填充。
TINYINT[(M)] [UNSIGNED] [ZEROFILL] A very small integer. The signed range is -128 to 127. The unsigned range is 0 to 255. INT[(M)] [UNSIGNED] [ZEROFILL] A normal-size integer. The signed range is -2147483648 to 2147483647. The unsigned range is 0 to 4294967295. 位数限制基本没有意义。mysql> create table testint(id int(1), col2 tinyint(1)); Query OK, 0 rows affected (0.06 sec)mysql> insert into testint values(256, 257); Query OK, 1 row affected, 1 warning (0.03 sec)mysql> select * from testint; +------+------+ | id | col2 | +------+------+ | 256 | 127 | +------+------+ 1 row in set (0.02 sec)mysql> insert into testint values(336, 257); Query OK, 1 row affected, 1 warning (0.02 sec)mysql> select * from testint; +------+------+ | id | col2 | +------+------+ | 256 | 127 | | 336 | 127 | +------+------+ 2 rows in set (0.00 sec)mysql> insert into testint values(336, 255); Query OK, 1 row affected, 1 warning (0.03 sec)mysql> select * from testint; +------+------+ | id | col2 | +------+------+ | 256 | 127 | | 336 | 127 | | 336 | 127 | +------+------+ 3 rows in set (0.00 sec)mysql>关注一下上边的warning提示。
如int(3),如果实际值是2,如果列指定了zerofill,查询结果就是002,左边用0来填充。
位数限制基本没有意义。mysql> create table testint(id int(1), col2 tinyint(1));
Query OK, 0 rows affected (0.06 sec)mysql> insert into testint values(256, 257);
Query OK, 1 row affected, 1 warning (0.03 sec)mysql> select * from testint;
+------+------+
| id | col2 |
+------+------+
| 256 | 127 |
+------+------+
1 row in set (0.02 sec)mysql> insert into testint values(336, 257);
Query OK, 1 row affected, 1 warning (0.02 sec)mysql> select * from testint;
+------+------+
| id | col2 |
+------+------+
| 256 | 127 |
| 336 | 127 |
+------+------+
2 rows in set (0.00 sec)mysql> insert into testint values(336, 255);
Query OK, 1 row affected, 1 warning (0.03 sec)mysql> select * from testint;
+------+------+
| id | col2 |
+------+------+
| 256 | 127 |
| 336 | 127 |
| 336 | 127 |
+------+------+
3 rows in set (0.00 sec)mysql>关注一下上边的warning提示。