MySQL 5.7升级8.0后出现排序规则问题的解决方案汇总
比较操作中使用不同的字符集或排序规则通常会触发此问题，MySQL 8.0 默认 COLLATE 为 utf8mb4_0900_ai_ci 和 对应列 COLLATE 的 utf8mb4_general_ci 不匹配。问题现象
MySQL 5.7.34 升级到 8.0.32 后部分查询语句报错如下：
ERROR 1267 (HY000): Illegal mix of collations (utf8mb4_general_ci,IMPLICIT) and (utf8mb4_0900_ai_ci,IMPLICIT) for operation 'find_in_set'
问题原因
比较操作中使用不同的字符集或排序规则通常会触发此问题，MySQL 8.0 默认 COLLATE 为 utf8mb4_0900_ai_ci 和 对应列 COLLATE 的 utf8mb4_general_ci 不匹配。
问题重现过程
创建测试表。
CREATE TABLE `t01` (
`ID` varchar(30) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL,
`A_CODE` varchar(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL,
`B_CODE` varchar(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL,
PRIMARY KEY (`ID`) USING BTREE
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci ROW_FORMAT=DYNAMIC;执行查询语句。
SELECT AAA.* FROM(
SELECT
@xxx AS _xxx,
( SELECT @xxx := GROUP_CONCAT( A_CODE ) FROM t01 WHERE FIND_IN_SET( B_CODE, @xxx ) ) AS cxxx
FROM
t01,( SELECT @xxx := 'xxx') b
WHERE @xxx IS NOT NULL) ID,t01 AAA
WHERE
FIND_IN_SET( AAA.A_CODE, ID._xxx )
order by A_CODE;报错。
ERROR 1267 (HY000): Illegal mix of collations (utf8mb4_general_ci,IMPLICIT) and (utf8mb4_0900_ai_ci,IMPLICIT) for operation 'find_in_set'
问题分析
查看默认排序规则。
mysql> show collation like 'utf8mb4_0900_ai_ci';
+--------------------+---------+-----+---------+----------+---------+---------------+
| Collation | Charset | Id| Default | Compiled | Sortlen | Pad_attribute |
+--------------------+---------+-----+---------+----------+---------+---------------+
| utf8mb4_0900_ai_ci | utf8mb4 | 255 | Yes | Yes | 0 | NO PAD |
+--------------------+---------+-----+---------+----------+---------+---------------+
1 row in set (0.00 sec)
mysql> show collation like 'utf8mb4_general_ci';
+--------------------+---------+----+---------+----------+---------+---------------+
| Collation | Charset | Id | Default | Compiled | Sortlen | Pad_attribute |
+--------------------+---------+----+---------+----------+---------+---------------+
| utf8mb4_general_ci | utf8mb4 | 45 | | Yes | 1 | PAD SPACE |
+--------------------+---------+----+---------+----------+---------+---------------+
1 row in set (0.00 sec)
mysql> SELECT * FROM INFORMATION_SCHEMA.COLLATIONS WHERE IS_DEFAULT='Yes' and CHARACTER_SET_NAME='utf8mb4';
+--------------------+--------------------+-----+------------+-------------+---------+---------------+
| COLLATION_NAME | CHARACTER_SET_NAME | ID| IS_DEFAULT | IS_COMPILED | SORTLEN | PAD_ATTRIBUTE |
+--------------------+--------------------+-----+------------+-------------+---------+---------------+
| utf8mb4_0900_ai_ci | utf8mb4 | 255 | Yes | Yes | 0 | NO PAD |
+--------------------+--------------------+-----+------------+-------------+---------+---------------+
1 row in set (0.00 sec)查看相关参数。
mysql> show variables like '%collation%';
+-------------------------------+--------------------+
| Variable_name | Value |
+-------------------------------+--------------------+
| collation_connection | utf8mb4_0900_ai_ci |
| collation_database | utf8mb4_general_ci |
| collation_server | utf8mb4_general_ci |
| default_collation_for_utf8mb4 | utf8mb4_0900_ai_ci |
+-------------------------------+--------------------+
4 rows in set (0.00 sec)
其中:
mysql> show global variables like '%collation%';
+-------------------------------+--------------------+
| Variable_name | Value |
+-------------------------------+--------------------+
| collation_connection | utf8mb4_general_ci |
| collation_database | utf8mb4_general_ci |
| collation_server | utf8mb4_general_ci |
| default_collation_for_utf8mb4 | utf8mb4_0900_ai_ci |
+-------------------------------+--------------------+
4 rows in set (0.00 sec)查看配置文件参数。
mysql@CJC-DB-01:/home/mysql$cat /etc/my.cnf
......
collation_server = utf8mb4_general_ci可以看到，客户端局部会话变量 collation_connection 的值为 utf8mb4_0900_ai_ci，而全局变量值为 utf8mb4_general_ci，两者不一致。
这是由于服务端在客户端连接时，获取了客户端对字符集和排序规则的缺省设置，也就是 utf8mb4_0900_ai_ci。
解决方案
[*]修改参数
[*]修改表 COLLATE
[*]修改 SQL 语句
1. 修改参数
参数collation_connection 在客户端局部变量值和全局变量值不一致，如何改成一致？官网参考材料
--character-set-client-handshake
Command-Line Format:--character-set-client-handshake[={OFF|ON}]
Deprecated:8.0.35
Type:Boolean
Default Value:ON
参数说明
[*]不忽略客户端发送的字符集信息
[*]为了忽略客户端信息并使用默认的服务器字符集
[*]使用参数：--skip-character-set-client-handshake
此选项在 MySQL 8.0.35 及更高版本的 MySQL 8.0 中已被弃用。在该版本中，无论何时使用此选项，都会发出警告，并将在未来版本的 MySQL 中删除。
依赖此选项的应用程序应该尽快开始迁移。
添加 my.cnf 参数。
skip-character-set-client-handshake重启 MySQL。
mysqladmin -uroot -p****** shutdown
mysqld --defaults-file=/etc/my.cnf --user=mysql &
登录
mysql -uroot -p cjc
查看参数，collation_connection 参数值修改成功
mysql> show global variables like '%collation%';
+-------------------------------+--------------------+
| Variable_name | Value |
+-------------------------------+--------------------+
| collation_connection | utf8mb4_general_ci |
| collation_database | utf8mb4_general_ci |
| collation_server | utf8mb4_general_ci |
| default_collation_for_utf8mb4 | utf8mb4_0900_ai_ci |
+-------------------------------+--------------------+
4 rows in set (0.00 sec)
mysql> show variables like '%collation%';
+-------------------------------+--------------------+
| Variable_name | Value |
+-------------------------------+--------------------+
| collation_connection | utf8mb4_general_ci |
| collation_database | utf8mb4_general_ci |
| collation_server | utf8mb4_general_ci |
| default_collation_for_utf8mb4 | utf8mb4_0900_ai_ci |
+-------------------------------+--------------------+
4 rows in set (0.01 sec)再次执行，问题解决。
SELECT AAA.* FROM(
SELECT
@xxx AS _xxx,
( SELECT @xxx := GROUP_CONCAT( A_CODE ) FROM t01 WHERE FIND_IN_SET( B_CODE, @xxx ) ) AS cxxx
FROM
t01,( SELECT @xxx := 'xxx') b
WHERE @xxx IS NOT NULL) ID,t01 AAA
WHERE
FIND_IN_SET( AAA.A_CODE, ID._xxx )
order by A_CODE;Empty set, 2 warnings (0.00 sec)
2. 修改表 COLLATE
先改回原参数，查询报错。
SELECT AAA.* FROM(
SELECT
@xxx AS _xxx,
( SELECT @xxx := GROUP_CONCAT( A_CODE ) FROM t01 WHERE FIND_IN_SET( B_CODE, @xxx ) ) AS cxxx
FROM
t01,( SELECT @xxx := 'xxx') b
WHERE @xxx IS NOT NULL) ID,t01 AAA
WHERE
FIND_IN_SET( AAA.A_CODE, ID._xxx )
order by A_CODE;ERROR 1267 (HY000): Illegal mix of collations (utf8mb4_general_ci,IMPLICIT) and (utf8mb4_0900_ai_ci,IMPLICIT) for operation 'find_in_set'修改表排序规则。
mysql> show create table t01\G;
*************************** 1. row ***************************
Table: t01
Create Table: CREATE TABLE `t01` (
`ID` varchar(30) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL,
`A_CODE` varchar(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL,
`B_CODE` varchar(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL,
PRIMARY KEY (`ID`) USING BTREE
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci ROW_FORMAT=DYNAMIC
1 row in set (0.00 sec)
ERROR:
No query specified修改所有列 COLLATE，实际上只修改 A_CODE、B_CODE 列 COLLATE 也可解决此问题。
ALTER TABLE cjc.t01 DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;
ALTER TABLE cjc.t01 MODIFY COLUMN `ID` varchar(30) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NOT NULL;
ALTER TABLE cjc.t01 MODIFY COLUMN `A_CODE` varchar(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci DEFAULT NULL;
ALTER TABLE cjc.t01 MODIFY COLUMN `B_CODE` varchar(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci DEFAULT NULL;再次执行，问题解决。
SELECT AAA.* FROM(
SELECT
@xxx AS _xxx,
( SELECT @xxx := GROUP_CONCAT( A_CODE ) FROM t01 WHERE FIND_IN_SET( B_CODE, @xxx ) ) AS cxxx
FROM
t01,( SELECT @xxx := 'xxx') b
WHERE @xxx IS NOT NULL) ID,t01 AAA
WHERE
FIND_IN_SET( AAA.A_CODE, ID._xxx )
order by A_CODE;Empty set, 2 warnings (0.00 sec)查看表结构。
mysql> show create table t01\G;
*************************** 1. row ***************************
Table: t01
Create Table: CREATE TABLE `t01` (
`ID` varchar(30) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NOT NULL,
`A_CODE` varchar(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci DEFAULT NULL,
`B_CODE` varchar(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci DEFAULT NULL,
PRIMARY KEY (`ID`) USING BTREE
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci ROW_FORMAT=DYNAMIC
1 row in set (0.00 sec)
3. 修改 SQL 语句
将 A_CODE，B_CODE 列的 COLLATE 在 SQL 语句中转换为 utf8mb4_0900_ai_ci。
改写后的SQL如下：
SELECT AAA.* FROM(
SELECT
@xxx AS _xxx,
( SELECT @xxx := GROUP_CONCAT( A_CODE COLLATE utf8mb4_0900_ai_ci ) FROM t01 WHERE FIND_IN_SET( B_CODE COLLATE utf8mb4_0900_ai_ci, @xxx ) ) AS cxxx
FROM
t01,( SELECT @xxx := 'xxx') b
WHERE @xxx IS NOT NULL) ID,t01 AAA
WHERE
FIND_IN_SET( AAA.A_CODE COLLATE utf8mb4_0900_ai_ci, ID._xxx )
order by A_CODE;
总结
比较三种解决方案，每种解决方案适用场景不同，请根据实际情况选择解决方案。
[*]修改参数
适用于数据库是从 5.7 或更低版本升级到 8.0，并且表数量较多、数据量加大。不适用于批量修改所有表、列字符集和排序规则。
[*]修改表 COLLATE
适用于修改过程会锁表，数据量越大时间越长，使用于数据量小的场景，建议将所有表、列字符集和排序规则改成 8.0 默认值，后续新增表时不指定字符集和排序规则。
[*]修改 SQL 语句
适用于临时查询，改SQL影响最小。
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