mysql int(1) tinyint(1)有什么区别?
我指定了字段长度,类型还有意义吗?

 

Reply:

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。。。。

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mysql   中   真，假   这样的数据应该用什么数据类型?

reply:tinyint(1)

 

可参考： http://database.51cto.com/art/201203/323863.htm