关于【SQL优化】中的【不要让数据库帮我们做强制类型转换】和【如果需要进行 join，两表的字段类型要相同】的一点疑问

Using where; Using index interpretation:

• Using index, the query does not need to return data, but can be obtained directly through the index. If using where is also present, it means that the index is used to find the value, and there is no using