An SQL query problem

I want to sort and query the top five comments by the number of comments in the article. There are two tables, the article table and the comment table. I used internal connections, the results are all public parts, so the filtered results must contain comments. if the number of comments is 0, nothing can be found. what I want is not... I want to sort the number of comments in the article and query the first five comments. There are two tables, the article table and
In the comment table, we used an inner join to obtain all the public parts. Therefore, the filtered result must have a comment volume. if the comment volume is 0, I don't want such a result. my requirement is that even if the number of comments is 0, I can participate in the sorting. I checked it online and should use the full connection, however, an error is reported and a test is conducted. it seems that all connections will report an error.
The following code uses thinkphp
$ HotArticle = $ articleModel-> join ('sys _ comment on sys_comment.article_id = sys_article.article_id ', 'full')-> field ('sys _ article. , Count () As num')-> group ('sys _ article. article_id ')-> order ('count (*) desc')-> limit (5)-> select ();