MySQL:在查询中整理 - 任何副作用？

Question

不幸的OpenCart是utf8_bin,我的表格整理是无法搜索名称中带有重音的产品名称.我在谷歌搜索,发现校对必须是utf8_general_ci兼容重音和不区分大小写的搜索.

如果我在搜索查询中添加整理声明怎么办？

SELECT * 
FROM  `address` 
COLLATE utf8_general_ci
LIMIT 0 , 30

它有任何(坏)副作用吗？我是关于索引,性能的问题？还是完全安全的？

Answer 1

恐怕您必须考虑对查询性能的副作用，尤其是那些使用索引的查询。这是一个简单的测试：

mysql> create table aaa (a1 varchar(100) collate latin1_general_ci, tot int);
insert into aaa values('test1',3) , ('test2',4), ('test5',5);

mysql> create index aindex on aaa (a1);
Query OK, 0 rows affected (0.59 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc aaa;
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| a1    | varchar(100) | YES  | MUL | NULL    |       |
| tot   | int(11)      | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+
2 rows in set (0.53 sec)


mysql> explain select * from aaa where a1='test1' ;
+----+-------------+-------+------+---------------+--------+---------+-------+--
----+-----------------------+
| id | select_type | table | type | possible_keys | key    | key_len | ref   | r
ows | Extra                 |
+----+-------------+-------+------+---------------+--------+---------+-------+--
----+-----------------------+
|  1 | SIMPLE      | aaa   | ref  | aindex        | aindex | 103     | const |
  1 | Using index condition |
+----+-------------+-------+------+---------------+--------+---------+-------+--
----+-----------------------+
1 row in set (0.13 sec)

mysql> explain select * from aaa where a1='test1' collate utf8_general_ci;
+----+-------------+-------+------+---------------+------+---------+------+-----
-+-------------+
| id | select_type | table | type | possible_keys | key  | key_len | ref  | rows
 | Extra       |
+----+-------------+-------+------+---------------+------+---------+------+-----
-+-------------+
|  1 | SIMPLE      | aaa   | ALL  | NULL          | NULL | NULL    | NULL |    3
 | Using where |
+----+-------------+-------+------+---------------+------+---------+------+-----
-+-------------+
1 row in set (0.06 sec)

您可以看到，当您使用其他排序规则搜索 a1 时，MySQL 停止使用 a1 上的索引，这对您来说可能是一个大问题。

为了确保索引用于查询，您可能必须将列排序规则更改为最常用的排序规则。