SQL函数按最流行的内容排序

I don't know if this is possible with SQL: I have two tables, one of content, each with an integer ID, and a table of comments each with an "On" field denoting the content it is on. I'd like to receive the content in order of how many comments have it in their "On" field, and was hoping SQL could do it.I don't know if this is possible with SQL: I ha