先看一下MySQL支持的整型数及大小，存储空间:
| pe | Storage | Minimum Value | Maximum Value | 存储大小 |
|---|---|---|---|---|
| (Bytes) | (Signed/Unsigned) | (Signed/Unsigned) | byte | |
| TINYINT | 1 | -128 | 127 | 1 byte |
| 0 | 255 | |||
| SMALLINT | 2 | -32768 | 32767 | 2 bytes |
| 0 | 65535 | |||
| MEDIUMINT | 3 | -8388608 | 8388607 | 3 bytes |
| 0 | 16777215 | |||
| INT | 4 | -21474838 | 21474837 | 4 bytes |
| 0 | 4294967295 | |||
| BIGINT | 8 | -9223372036854775808 | 9223372036854775807 | 8 bytes |
| 0 | 18446744073709551615 |
另外请记着mysql的数据处理会转成bigint处理，所以这里就用bigint几个测试：
代码如下:
SELECT CAST(0 AS UNSIGNED) - 1;
SELECT 9223372036854775807 + 1;
MySQL 5.1 下：
代码如下:
mysql> SELECT CAST(0 AS UNSIGNED) - 1;
+-------------------------+
| CAST(0 AS UNSIGNED) - 1 |
+-------------------------+
| 18446744073709551615 |
+-------------------------+
1 row in set (0.01 sec)
mysql> SELECT 9223372036854775807 + 1;
+-------------------------+
| 9223372036854775807 + 1 |
+-------------------------+
| -9223372036854775808 |
+-------------------------+
1 row in set (0.01 sec)
MySQL 5.5, 5.6, 5.7下：
代码如下:
mysql> SELECT CAST(0 AS UNSIGNED) - 1;
ERROR 1690 (22003): BIGINT UNSIGNED value is out of range in '(cast(0 as unsigned) - 1)'
mysql>
mysql>
mysql>
mysql> SELECT 9223372036854775807 + 1;
ERROR 1690 (22003): BIGINT value is out of range in '(9223372036854775807 + 1)'
所在处理这类数据是一定要小心溢出（如早期有做弊冲Ｑ币就是利用这个方法处理）
这个问题有可能会出现积分消息，积分相加， 或是一些钱相关的业务中出现, 主库5.1 ，从库MySQL 5.5情况也会出现不同步的问题。
建议：这类业务系统尽可能的升级到MySQL 5.5后版本
更多详情参考： http://dev.mysql.com/doc/refman/5.7/en/out-of-range-and-overflow.html
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