mysql多表join时报错如下：[err]1267 – illegal mix of collations(utf8_general_ci,implicit) and (utf8_unicode_ci,implicit) for operation ‘=
就是说两个表的排序规则（COLLATION）不同，无法完成比较。COLLATION是用在排序，大小比较上，一个字符集有一个或多种COLLATION，并且以_ci（大小写不敏感）、_cs（大小写敏感）或_bin（二进制）结束。在做比较时，应该确保两个表的字符排序相同。一般建表的时候不指定，可以走默认的，全是默认的就没什么问题了。本文主要介绍了MySQL表排序规则不同错误问题分析，希望能帮助到大家。
下面来模拟一下各种场景，表结构如下（utf8默认排序规则为utf8_general_ci）：
mysql> show create table test.csG*************************** 1. row *************************** Table: csCreate Table: CREATE TABLE `cs` ( `id` int(11) DEFAULT NULL, `name` varchar(10) DEFAULT NULL) ENGINE=InnoDB DEFAULT CHARSET=utf81 row in set (0.01 sec)
查看表默认排序规则集
mysql> select TABLE_SCHEMA,TABLE_NAME,TABLE_COLLATION from information_schema.tables where table_name='cs';+--------------+------------+-----------------+| TABLE_SCHEMA | TABLE_NAME | TABLE_COLLATION |+--------------+------------+-----------------+| test | cs | utf8_general_ci |+--------------+------------+-----------------+1 row in set (0.00 sec)
查看列排序规则集
mysql> select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME,COLLATION_NAME from information_schema.COLUMNS where TABLE_NAME='cs';+--------------+------------+-------------+-----------------+| TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME | COLLATION_NAME |+--------------+------------+-------------+-----------------+| test | cs | id | NULL || test | cs | name | utf8_general_ci |+--------------+------------+-------------+-----------------+2 rows in set (0.00 sec)
从utf8升级为utf8mb4是不支持online ddl的，如下：
mysql> ALTER TABLE cs CONVERT TO CHARACTER SET utf8mb4,ALGORITHM=INPLACE,LOCK=NONE;ERROR 1846 (0A000): ALGORITHM=INPLACE is not supported. Reason: Cannot change column type INPLACE. Try ALGORITHM=COPY.
从utf8.utf8_general_ci变更为utf8.utf8_unicode_ci是不支持online ddl的，如下：
mysql> ALTER TABLE cs CONVERT TO CHARACTER SET utf8 collate utf8_unicode_ci,ALGORITHM=INPLACE,LOCK=NONE;ERROR 1846 (0A000): ALGORITHM=INPLACE is not supported. Reason: Cannot change column type INPLACE. Try ALGORITHM=COPY.
如果使用下面这种方式修改字符集，你会发现，只更改了表级的，没有更改列级的。
mysql> ALTER TABLE cs CHARACTER SET utf8 collate utf8_unicode_ci; Query OK, 0 rows affected (0.01 sec)Records: 0 Duplicates: 0 Warnings: 0 mysql> select TABLE_SCHEMA,TABLE_NAME,TABLE_COLLATION from information_schema.tables where table_name='cs'; +--------------+------------+-----------------+| TABLE_SCHEMA | TABLE_NAME | TABLE_COLLATION |+--------------+------------+-----------------+| test | cs | utf8_unicode_ci |+--------------+------------+-----------------+1 row in set (0.00 sec) mysql> select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME,COLLATION_NAME from information_schema.COLUMNS where TABLE_NAME='cs';+--------------+------------+-------------+-----------------+| TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME | COLLATION_NAME |+--------------+------------+-------------+-----------------+| test | cs | id | NULL || test | cs | name | utf8_general_ci |+--------------+------------+-------------+-----------------+2 rows in set (0.00 sec)
所以真正改字符集的时候别忘了加上CONVERT TO，如下：
猫眼课题宝
5分钟定创新选题，3步生成高质量标书！
85 查看详情 
mysql> ALTER TABLE cs CONVERT TO CHARACTER SET utf8 collate utf8_unicode_ci;Query OK, 5 rows affected (0.06 sec)Records: 5 Duplicates: 0 Warnings: 0 mysql> select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME,COLLATION_NAME from information_schema.COLUMNS where TABLE_NAME='cs';+--------------+------------+-------------+-----------------+| TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME | COLLATION_NAME |+--------------+------------+-------------+-----------------+| test | cs | id | NULL || test | cs | name | utf8_unicode_ci |+--------------+------------+-------------+-----------------+2 rows in set (0.00 sec)
要仅仅改变一个表的默认字符集，应使用此语句：
mysql> ALTER TABLE cs default CHARACTER SET utf8 collate utf8_general_ci,ALGORITHM=INPLACE,LOCK=NONE; Query OK, 0 rows affected (0.00 sec)Records: 0 Duplicates: 0 Warnings: 0 mysql> select TABLE_SCHEMA,TABLE_NAME,TABLE_COLLATION from information_schema.tables where table_name='cs'; +--------------+------------+-----------------+| TABLE_SCHEMA | TABLE_NAME | TABLE_COLLATION |+--------------+------------+-----------------+| test | cs | utf8_general_ci |+--------------+------------+-----------------+1 row in set (0.00 sec) mysql> select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME,COLLATION_NAME from information_schema.COLUMNS where TABLE_NAME='cs'; +--------------+------------+-------------+-----------------+| TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME | COLLATION_NAME |+--------------+------------+-------------+-----------------+| test | cs | id | NULL || test | cs | name | utf8_unicode_ci |+--------------+------------+-------------+-----------------+2 rows in set (0.00 sec)
可以发现列字符集没有改变，并且只有新的列才会默认继承表的字符集（utf8.utf8_general_ci）。
相关推荐：
MySQL表的四种分区类型的代码详解
如何使用mysql表连接
php mysql表中文乱码问题如何解决
以上就是MySQL表排序规则不同报错问题分析的详细内容，更多请关注创想鸟其它相关文章！
版权声明：本文内容由互联网用户自发贡献，该文观点仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。
如发现本站有涉嫌抄袭侵权/违法违规的内容， 请发送邮件至 chuangxiangniao@163.com 举报，一经查实，本站将立刻删除。
发布者：程序猿，转转请注明出处：https://www.chuangxiangniao.com/p/387002.html
微信扫一扫 
支付宝扫一扫 
