ASCII(str)

返回字符串str的最左字符的數值。返回0，如果str為空字符串。返回NULL，如果str為NULL。 ASCII()返回數值是從0到255。

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

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