若依系统安装配置后，点击“系统工具-代码生成-导入”时报错：

### Error querying database. 
Cause: java.sql.SQLException: Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8_unicode_ci,IMPLICIT) for operation '=' 
### The error may exist in file [E:\test\RuoYi-Vue\ruoyi-generator\target\classes\mapper\generator\GenTableMapper.xml] 
### The error may involve com.ruoyi.generator.mapper.GenTableMapper.selectDbTableList-Inline 
### The error occurred while setting parameters 
### SQL: SELECT count(0) FROM information_schema.tables WHERE table_schema = (SELECT database()) AND table_name NOT LIKE 'qrtz_%' AND table_name NOT LIKE 'gen_%' AND table_name NOT IN (SELECT table_name FROM gen_table) 
### Cause: java.sql.SQLException: Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8_unicode_ci,IMPLICIT) for operation '=' ; 
uncategorized SQLException; SQL state [HY000]; error code [1267]; 
Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8_unicode_ci,IMPLICIT) for operation '='; 
nested exception is java.sql.SQLException: Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8_unicode_ci,IMPLICIT) for operation '='

看上去是两个表的字段的编码不同的问题，检查了若依的所有表，发现都统一是utf8_unicode_ci，没有问题。

仔细看了报错信息，是下面的sql语问的出错。

SELECT count(0) FROM information_schema.tables WHERE table_schema = (SELECT database()) AND table_name NOT LIKE 'qrtz_%' AND table_name NOT LIKE 'gen_%' AND table_name NOT IN (SELECT table_name FROM gen_table)

是mysql自带的表information_schema.tables，与若依系统的表进行了关联查询。
而information_schema用的是utf8_general_ci编码排序，若依建数据库时，默认选了utf8_unicode_ci。

• 于是，重建若依数据库，使用utf8_general_ci编码。

• 问题解决。

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注：utf8_general_ci和utf8_unicode_ci的区别
https://blog.csdn.net/testcs_dn/article/details/70157144
看了一下，对于中文和英文，两种排序规则差别不大，utf8_general_ci还更快一点。