英语不是我的母语；请原谅输入错误。
我正在使用 5.5.38-MariaDB。 Mysql语句:
SELECT CAST(11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111
AS char);
我得到的结果是999999999999999999999999999999999999999999999999999999999999999999，为什么？
更新:
MariaDB [(none)]> SELECT CAST(199999999999999999999999999999999999999999999999999999999999999999999999999999999 AS char);
+-------------------------------------------------------------------------------------------------+
| CAST(199999999999999999999999999999999999999999999999999999999999999999999999999999999 AS char) |
+-------------------------------------------------------------------------------------------------+
| 199999999999999999999999999999999999999999999999999999999999999999999999999999999 |
+-------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
MariaDB [(none)]> SELECT CAST(1999999999999999999999999999999999999999999999999999999999999999999999999999999999 AS char);
+--------------------------------------------------------------------------------------------------+
| CAST(1999999999999999999999999999999999999999999999999999999999999999999999999999999999 AS char) |
+--------------------------------------------------------------------------------------------------+
| 99999999999999999999999999999999999999999999999999999999999999999 |
+--------------------------------------------------------------------------------------------------+
1 row in set, 1 warning (0.01 sec)
MariaDB [(none)]> SHOW WARNINGS;
+---------+------+--------------------------------------------------------------+
| Level | Code | Message |
+---------+------+--------------------------------------------------------------+
| Warning | 1916 | Got overflow when converting '' to DECIMAL. Value truncated. |
+---------+------+--------------------------------------------------------------+
1 row in set (0.00 sec)
最佳答案
1111... 被解析为数字，具体为 DECIMAL(65, ...)。最大为 65；因为这个东西比这个大，所以它给了你 65 个 9。它给了你一个警告(可能被忽略):
mysql> SELECT CAST(11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111 AS CHAR) AS too_big;
+-------------------------------------------------------------------+
| too_big |
+-------------------------------------------------------------------+
| 99999999999999999999999999999999999999999999999999999999999999999 |
+-------------------------------------------------------------------+
1 row in set, 1 warning (0.00 sec)
mysql> SHOW WARNINGS;
+---------+------+---------------------------------------+
| Level | Code | Message |
+---------+------+---------------------------------------+
| Warning | 1292 | Truncated incorrect DECIMAL value: '' |
+---------+------+---------------------------------------+
1 row in set (0.00 sec)
你希望得到什么？
关于mysql 将大数转换为字符，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/53531101/