我有一个函数,返回5个混合大小写字符。如果我对这个字符串进行查询,不管大小写,它都会返回值。

如何使MySQL字符串查询区分大小写?


当前回答

要在使用BINARY之前使用索引,如果有大型表,可以这样做。

SELECT
   *
FROM
   (SELECT * FROM `table` WHERE `column` = 'value') as firstresult
WHERE
   BINARY `column` = 'value'

子查询将生成一个非常小的不区分大小写的子集,然后选择其中唯一区分大小写的匹配项。

其他回答

对于那些希望使用RLIKE或REGEXP与正则表达式进行区分大小写的比较的人来说,你可以使用REGEXP_LIKE()来匹配匹配类型c,如下所示:

SELECT * FROM `table` WHERE REGEXP_LIKE(`column`, 'value', 'c');

您可以像这样使用二进制区分大小写

select * from tb_app where BINARY android_package='com.Mtime';

不幸的是,此SQL不能使用索引,依赖于该索引的查询将遭受性能损失

mysql> explain select * from tb_app where BINARY android_package='com.Mtime';
+----+-------------+--------+------------+------+---------------+------+---------+------+---------+----------+-------------+
| id | select_type | table  | partitions | type | possible_keys | key  | key_len | ref  | rows    | filtered | Extra       |
+----+-------------+--------+------------+------+---------------+------+---------+------+---------+----------+-------------+
|  1 | SIMPLE      | tb_app | NULL       | ALL  | NULL          | NULL | NULL    | NULL | 1590351 |   100.00 | Using where |
+----+-------------+--------+------------+------+---------------+------+---------+------+---------+----------+-------------+

幸运的是,我有一些技巧来解决这个问题

mysql> explain select * from tb_app where android_package='com.Mtime' and BINARY android_package='com.Mtime';
+----+-------------+--------+------------+------+---------------------------+---------------------------+---------+-------+------+----------+-----------------------+
| id | select_type | table  | partitions | type | possible_keys             | key                       | key_len | ref   | rows | filtered | Extra                 |
+----+-------------+--------+------------+------+---------------------------+---------------------------+---------+-------+------+----------+-----------------------+
|  1 | SIMPLE      | tb_app | NULL       | ref  | idx_android_pkg           | idx_android_pkg           | 771     | const |    1 |   100.00 | Using index condition |
+----+-------------+--------+------------+------+---------------------------+---------------------------+---------+-------+------+----------+-----------------------+  

要在使用BINARY之前使用索引,如果有大型表,可以这样做。

SELECT
   *
FROM
   (SELECT * FROM `table` WHERE `column` = 'value') as firstresult
WHERE
   BINARY `column` = 'value'

子查询将生成一个非常小的不区分大小写的子集,然后选择其中唯一区分大小写的匹配项。

克雷格·怀特(Craig White)发布的答案有很大的性能损失

SELECT *  FROM `table` WHERE BINARY `column` = 'value'

因为它不使用索引。所以,要么你需要像这里提到的那样改变表的排序规则https://dev.mysql.com/doc/refman/5.7/en/case-sensitivity.html。

OR

最简单的解决方法,你应该使用二进制值。

SELECT *  FROM `table` WHERE `column` = BINARY 'value'

E.g.

mysql> EXPLAIN SELECT * FROM temp1 WHERE BINARY col1 = "ABC" AND col2 = "DEF" ;
+----+-------------+--------+------+---------------+------+---------+------+--------+-------------+
| id | select_type | table  | type | possible_keys | key  | key_len | ref  | rows   | Extra       |
+----+-------------+--------+------+---------------+------+---------+------+--------+-------------+
|  1 | SIMPLE      | temp1  | ALL  | NULL          | NULL | NULL    | NULL | 190543 | Using where |
+----+-------------+--------+------+---------------+------+---------+------+--------+-------------+

VS

mysql> EXPLAIN SELECT * FROM temp1 WHERE col1 = BINARY "ABC" AND col2 = "DEF" ;
+----+-------------+-------+-------+---------------+---------------+---------+------+------+------------------------------------+
| id | select_type | table | type  | possible_keys | key           | key_len | ref  | rows | Extra                              |
+----+-------------+-------+-------+---------------+---------------+---------+------+------+------------------------------------+
|  1 | SIMPLE      | temp1 | range | col1_2e9e898e | col1_2e9e898e | 93      | NULL |    2 | Using index condition; Using where |
+----+-------------+-------+-------+---------------+---------------+---------+------+------+------------------------------------+
enter code here

set中的1行(0.00秒)

太好了!

我和你们分享一个比较密码的函数的代码:

SET pSignal =
(SELECT DECODE(r.usignal,'YOURSTRINGKEY') FROM rsw_uds r WHERE r.uname =
in_usdname AND r.uvige = 1);

SET pSuccess =(SELECT in_usdsignal LIKE BINARY pSignal);

IF pSuccess = 1 THEN
      /*Your code if match*/
ELSE
      /*Your code if don't match*/

END IF;