MySQL數據庫的int(1)和tinyint(1)兩種數據類型有什么區別，那對他們指定了字段長度,類型還有意義嗎?
回答:
MySQL 中int(1)和tinyint(1)中的1只是指定顯示長度，并不表示存儲長度，只有字段指定zerofill是有用
如int(3)，如果實際值是2，如果列指定了zerofill，查詢結果就是002，左邊用0來填充。
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.
位數限制基本沒有意義。
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>
關注一下上邊的warning提示。。。。
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MySQL 中 真，假 這樣的數據應該用什么數據類型?
回答:tinyint(1)
