By default in MySQL, the where condition encounters a string is case-insensitive.
The results of the following two SQL statements are the same:
MySQL [datawarehouse]> select * from temp_01 t where browser = 'ie:11' limit 3;
+-----+----------+-----------+---------+--------+
| id | platform | version | browser | counts |
+-----+----------+-----------+---------+--------+
| 48 | 1 | website:1 | IE:11 | 70 |
| 117 | 20 | website:1 | IE:11 | 70 |
+-----+----------+-----------+---------+--------+
2 rows in set (0.01 sec)
MySQL [datawarehouse]> select * from temp_01 t where browser = 'IE:11' limit 3;
+-----+----------+-----------+---------+--------+
| id | platform | version | browser | counts |
+-----+----------+-----------+---------+--------+
| 48 | 1 | website:1 | IE:11 | 70 |
| 117 | 20 | website:1 | IE:11 | 70 |
+-----+----------+-----------+---------+--------+
2 rows in set (0.01 sec)
Solution one:
Add keywords after the string field when building the tableBINARY
--创建相同结果的表,将browser字段加上关键字BINARY
CREATE TABLE `temp_02` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`platform` int(10) DEFAULT NULL,
`version` varchar(50) DEFAULT NULL,
`browser` varchar(50) BINARY DEFAULT NULL,
`counts` int(11) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=181 DEFAULT CHARSET=utf8;
--将temp_01表的数据导入temp_02中
insert into temp_02(id, platform, version, browser, counts) select id, platform, version, browser, counts from temp_01;
The result of this query is completely different
MySQL [datawarehouse]> select * from temp_02 t where browser = 'ie:11' limit 3;
Empty set (0.00 sec)
;
MySQL [datawarehouse]> select * from temp_02 t where browser = 'IE:11' limit 3;
+-----+----------+-----------+---------+--------+
| id | platform | version | browser | counts |
+-----+----------+-----------+---------+--------+
| 48 | 1 | website:1 | IE:11 | 70 |
| 117 | 20 | website:1 | IE:11 | 70 |
+-----+----------+-----------+---------+--------+
2 rows in set (0.00 sec)
Solution two:
Add keywords before the query statement where conditional string field:BINARY
MySQL [datawarehouse]> select * from temp_01 t where BINARY browser = 'IE:11' and version = 'Website:1' limit 3;
+-----+----------+-----------+---------+--------+
| id | platform | version | browser | counts |
+-----+----------+-----------+---------+--------+
| 48 | 1 | website:1 | IE:11 | 70 |
| 117 | 20 | website:1 | IE:11 | 70 |
+-----+----------+-----------+---------+--------+
2 rows in set (0.00 sec)
MySQL [datawarehouse]> select * from temp_01 t where BINARY browser = 'IE:11' and BINARY version = 'Website:1' limit 3;
Empty set (0.00 sec)
Solution three:
Modify the field character set:
- utf8_general_ci ---case insensitive
- utf8_bin-case sensitive
MySQL [datawarehouse]> ALTER TABLE temp_01 MODIFY COLUMN browser VARCHAR(50) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL;
Query OK, 180 rows affected (0.01 sec)
Records: 180 Duplicates: 0 Warnings: 0
MySQL [datawarehouse]>
MySQL [datawarehouse]> select * from temp_01 t where browser = 'ie:11' limit 3;
Empty set (0.00 sec)