SQL question challenge (Contents)

Link to github

  Table: content_id | content_type (comment/ post) | target_id
           If it is comment，target_id is the userid who posts it.
           If it is post, then target_id is NULL.

DDL Scripts

CREATE TABLE contents(
  content_id int,
  content_type varchar(80),
  target_id varchar(80));

  INSERT INTO contents VALUES (1,'comment','u1');
  INSERT INTO contents VALUES (2,'post',NULL);
  INSERT INTO contents VALUES (3,'comment','u2');
  INSERT INTO contents VALUES (4,'post',NULL);
  INSERT INTO contents VALUES (5,'comment','u1');
  INSERT INTO contents VALUES (6,'comment','u1');
  INSERT INTO contents VALUES (7,'comment','u3');
  INSERT INTO contents VALUES (8,'post',NULL);
  INSERT INTO contents VALUES (9,'video','u1');
  INSERT INTO contents VALUES (10,'video','u3');
  INSERT INTO contents VALUES (11,'post',NULL);
  INSERT INTO contents VALUES (12,'photo','u1');
  INSERT INTO contents VALUES (13,'photo','u3');
  INSERT INTO contents VALUES (14,'photo','u1');
  INSERT INTO contents VALUES (15,'article','u3');

QUESTIONS

1)WHAT IS THE DISTRIBUTION OF COMMENTS?

select a.cnt,count(a.cnt) as freq 
  from (select content_id, count(target_id) as cnt 
    from contents 
    where content_type='comment' 
    group by content_id
    ) a 
  group by a.cnt;
  +-----+------+
  | cnt | freq |
  +-----+------+
  |   1 |    5 |
  +-----+------+

2)DISTRIBUTION LIST OF EACH CONTENT TYPE #Now what if content_type becomes {comment, video, photo, article}，what is the comment distribution for each content type?

select a.cnt,a.content_type,count(a.cnt) freq 
  from (select content_id,content_type,count(target_id) as cnt 
     from contents 
     group by content_id,content_type
    ) a 
  group by a.cnt,a.content_type;
  +-----+--------------+------+
  | cnt | content_type | freq |
  +-----+--------------+------+
  |   1 | comment      |    5 |
  |   0 | post         |    4 |
  |   1 | video        |    2 |
  |   1 | photo        |    3 |
         |   1 | article      |    1 |
         +-----+--------------+------+