mysql - why this MySql regular expression not working?

Question

SELECT 'AaYYY1231' REGEXP '[A-Z,0-9]+';

Result:

1

Why is it returning 1, when I expect it to return 0 ? From where is is it finding match for 'a' ?

Answer 1

http://dev.mysql.com/doc/refman/5.1/en/regexp.html

“REGEXP 不区分大小写，除非与二进制字符串一起使用。”

文档中的一个例子：

mysql> SELECT 'a' REGEXP 'A', 'a' REGEXP BINARY 'A';
+----------------+-----------------------+
| 'a' REGEXP 'A' | 'a' REGEXP BINARY 'A' |
+----------------+-----------------------+
|              1 |                     0 |
+----------------+-----------------------+

此外，它不是贪婪的，因此它不能确保整个字符串匹配。修改上面的示例会产生：

mysql> SELECT 'a' REGEXP BINARY '[A-Z0-9]+', 'Aa' REGEXP BINARY '[A-Z0-9]+';
+-------------------------------+--------------------------------+
| 'a' REGEXP BINARY '[A-Z0-9]+' | 'Aa' REGEXP BINARY '[A-Z0-9]+' |
+-------------------------------+--------------------------------+
|                             0 |                              1 |
+-------------------------------+--------------------------------+

为了解决这个问题，您可以为行的开头和结尾添加标志：

mysql> SELECT 'Aa' REGEXP BINARY '^[A-Z0-9]+$';
+----------------------------------+
| 'Aa' REGEXP BINARY '^[A-Z0-9]+$' |
+----------------------------------+
|                                0 |
+----------------------------------+

这导致了您想要的最终答案：

mysql> SELECT 'AaYYY1231' REGEXP BINARY '^[A-Z,0-9]+$';
+------------------------------------------+
| 'AaYYY1231' REGEXP BINARY '^[A-Z,0-9]+$' |
+------------------------------------------+
|                                        0 |
+------------------------------------------+