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MySQL的类型转换

原创 Linux操作系统 作者:hquxiaoqi 时间:2011-11-08 16:19:44 0 删除 编辑
MySQL的类型转换函数如下:
CAST(expr AS type), CONVERT(expr,type), CONVERT(expr USING transcoding_name)
The type can be one of the following values:

BINARY[(N)]

CHAR[(N)]

DATE

DATETIME

DECIMAL

SIGNED [INTEGER]

TIME

UNSIGNED [INTEGER]
 
例:
mysql> set @temp=100.00;
Query OK, 0 rows affected (0.00 sec)
 
mysql> select @temp;
+--------+
| @temp  |
+--------+
| 100.00 |
+--------+
1 row in set (0.00 sec)
 
mysql> select cast(@temp as signed);
+-----------------------+
| cast(@temp as signed) |
+-----------------------+
|                   100 |
+-----------------------+
1 row in set (0.00 sec)
 
mysql> select cast(@temp as unsigned);
+-------------------------+
| cast(@temp as unsigned) |
+-------------------------+
|                     100 |
+-------------------------+
1 row in set (0.00 sec)
 
mysql> select convert(@temp,signed);
+-----------------------+
| convert(@temp,signed) |
+-----------------------+
|                   100 |
+-----------------------+
1 row in set (0.00 sec)
 
mysql> select convert(@temp,unsigned);
+-------------------------+
| convert(@temp,unsigned) |
+-------------------------+
|                     100 |
+-------------------------+
1 row in set (0.00 sec)
 
mysql> select '中文';
+------+
| 中文     |
+------+
| 中文     |
+------+
1 row in set (0.00 sec)
 
mysql> select convert('中文' using gb2312);
+------------------------------+
| convert('中文' using gb2312)     |
+------------------------------+
| ???                          |
+------------------------------+
1 row in set (0.02 sec)
 
mysql> select convert('中文' using utf8);
+----------------------------+
| convert('中文' using utf8)     |
+----------------------------+
| NULL                       |
+----------------------------+
1 row in set, 1 warning (0.00 sec)
MySQL配置为utf8字符集的,所以这儿将'中文'转化为utf8时会有警告.
 

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