记录一次sql语句执行错误：

left join表会出现 Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8_croatian_ci,IMPLICIT) for operation '='错误.

这是由于表的编码格式不一致 例如 某个表的字符编码为utf8_general_ci而关联表的字符编码为utf8_croatian_ci导致当前错误！

永久的

解决方案: 让关联表的字符编码一致

1.修改表中所有字符编码

ALTER TABLE 表名 CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8_general_ci;   

2…修改表的字符编码

ALTER TABLE 表名 DEFAULT CHARACTER SET utf8mb4 COLLATE utf8_general_ci;

此接口的

ON 后面加上 COLLATE utf8mb4_general_ci
解决方案实际应用

LEFT JOIN ( SELECT * FROM ( SELECT * FROM biz_task_queue ORDER BY create_date DESC LIMIT 10000 ) a GROUP BY relevance_id ) b ON a.id COLLATE utf8mb4_general_ci = b.relevance_id COLLATE utf8mb4_general_ci