在MySQL数据库中不同的整型的数据格式有不同的范围 。经常会出现数据类型溢出了（发生问题的版本是MySQL 5.1）。 这也让我有兴趣去了解一下MySQL不同版本数据类型溢出 的处理机制。
先看一下MySQL支持的整型数及大小，存储空间:
| | Type | 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 | -2147483648 | 2147483647 | 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：
SELECT CAST(0 AS UNSIGNED) - 1; SELECT 9223372036854775807 + 1;
SELECT CAST(0 AS UNSIGNED) - 1;
SELECT 9223372036854775807 + 1;
MySQL 5.1 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> 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：
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)'
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
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2015-5-5 15:42:52 |
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