Select-questions about querying duplicate data in mysql

I have a table named SC .! (Distinct) the score is queried with the same score. the query SQL statement is select * fromscwherescorein (selectscorefromscgroupbyscorehavingcount (score) & gt; 1 ); i'm curious that the execution order of groupby is better than having. in principle, the selectmysql image data SQL statement is executed.

I have a table named SC.

Now you want to query the information with the same score in the score,
The queried SQL statement is
Select * from SC where score in (select score from SC group by score having count (score)> 1 );

I'm curious that the execution sequence of group by is better than having,
According to the principle, the repeated score value after execution does not exist. how can we use having to find out count (score)> 1?
The duplicate score record .. Thank you.