在MySQL中比较“大于”和“小于”字符串安全吗?
MySQL 5.1.41-3ubuntu12.10-log似乎通过使用>大于和<小于给出了字符串比较的可预测结果:在MySQL中比较“大于”和“小于”字符串安全吗?,mysql,comparison,string-comparison,Mysql,Comparison,String Comparison,MySQL 5.1.41-3ubuntu12.10-log似乎通过使用>大于和
select "a" > "a", "a" > "b", "b" > "a", "ab" > "aa", "ab" > "aabbbb";
+-----------+-----------+-----------+-------------+-----------------+
| "a" > "a" | "a" > "b" | "b" > "a" | "ab" > "aa" | "ab" > "aabbbb" |
+-----------+-----------+-----------+-------------+-----------------+
| 0 | 0 | 1 | 1 | 1 |
+-----------+-----------+-----------+-------------+-----------------+
而且似乎还利用钥匙:
explain select productcode from products where productcode < 'no';
+----+-------------+----------+-------+-----------------+------+---------+------+------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+----------+-------+-----------------+------+---------+------+------+--------------------------+
| 1 | SIMPLE | products | range | productcode,ppp | ppp | 34 | NULL | 432 | Using where; Using index |
+----+-------------+----------+-------+-----------------+------+---------+------+------+--------------------------+
这似乎没有记录在案-这是可靠的跨平台功能吗?这些比较很常见。我确信跨平台支持通过ascii值或其他类似的编码来比较字符串。对不起,我没有任何资源来备份它。这可能就是它比较字符串进行排序的方式。我希望这是一个主要功能。我认为存在一些问题,您可以在这里查看文档以了解一些详细信息: 如果您的字段也有空值,还应查看空安全比较运算符: 例如:
mysql> select "a" > "a ", "A" > "a" , "aB" > "ab" , "a" >= NULL , "a" <=> NULL ;
+------------+-----------+--------------+-------------+--------------+
| "a" > "a " | "A" > "a" | "aB" > "ab" | "a" >= NULL | "a" <=> NULL |
+------------+-----------+--------------+-------------+--------------+
| 0 | 0 | 0 | NULL | 0 |
+------------+-----------+--------------+-------------+--------------+
第一个链接实际上没有关于比较这样的字符串的任何信息。