ASCII(str)

返回字符串str的最左字符的数值。如果str是空字符串返回0。如果str为NULL，返回NULL。ASCII()计算字符的数值范围为0至255。

mysql> SELECT ASCII('2');
+---------------------------------------------------------+
| ASCII('2')                                              |
+---------------------------------------------------------+
| 50                                                      |
+---------------------------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT ASCII('dx');
+---------------------------------------------------------+
| ASCII('dx')                                             |
+---------------------------------------------------------+
| 100                                                     |
+---------------------------------------------------------+
1 row in set (0.00 sec)