α数值列上的MySQL MIN & MAX

Question

简单的MAX查询：

SELECT MAX(Group) FROM acme

在数字列上工作正常。

是否可以在alpha-数值列上使用此方法而忽略数字以外的任何内容？

Answer 1

是的，如果你像这样在使用前铸造它

mysql> SELECT MAX(CAST("123" AS UNSIGNED));
+------------------------------+
| MAX(CAST("123" AS UNSIGNED)) |
+------------------------------+
|                          123 |
+------------------------------+
1 row in set (0.00 sec)

mysql> SELECT MAX(CAST("abc" AS UNSIGNED));
+------------------------------+
| MAX(CAST("abc" AS UNSIGNED)) |
+------------------------------+
|                            0 |
+------------------------------+
1 row in set, 1 warning (0.00 sec)

mysql> SELECT MAX(CAST("-123" AS SIGNED));
+-----------------------------+
| MAX(CAST("-123" AS SIGNED)) |
+-----------------------------+
|                        -123 |
+-----------------------------+
1 row in set (0.00 sec)

将字符串列名替换为"abc“，并根据请求修改查询。