这次产生问题的原因为nacos版本配置问题，当nacos版本为1.0.x的时候需要指定group，而我用的nacos版本为2.0.4不需要指定group，去掉group即可找到配置文件正常运行。服务启动有警告信息：Ignore the empty nacos configuration and get it based on dataId。可正常连接nacos，未报nacos连接错误信息。appl

Cause: java.lang.IllegalStateException: Type handler was null on parameter mapping forproperty 'urlParams'. It was either not specified and/or could not be found for the javaType(com.alibaba.fastjson.

public void main(String[] args) {//修改方法String unitId = "1";//将UnitCompanyCategory表下UnitId值为1对应的unitCategoryId字段数据改为1String categoryId = "1";LambdaUpdateWrapper<UnitCompanyCategory> lambdaUpdateW

问题：数据库提交代码时报Unable to resolve table ‘xxx‘错误解决方案：修改Idea配置打开idea下的Settings设置Inspaections查找sql配置Unresolved reference勾选去掉后保存可以正常提交代码

1、一张表中有username 字段数据重复，查询出username字段数据重复的所有数据，如下select * from table a where (a.username) in(select username from table group by usernamehaving count(*) > 1) order by username desc2、删除表中多余的重复记录，如下是删