计算列中具有相同值的行数

Question

I have these two entity with their attributes:

book - book_id, book_name, author_id, editor_id, subject_id, isbn

author - author_id, fn, ln

I have to query the author with the most number of rows here's the attributes and entity:

| book_id | book_name   | author_id |  editor_id |  isbn     |
--------------------------------------------------------------
|       1 | Book1 Title |  Author1  |  Editor1   | 8000-9000 |
|       2 | Book2 Title |  Author2  |  Editor1   | 8000-9001 |
|       1 | Book1 Title |  Author1  |  Editor1   | 8000-9002 |
|       3 | Book2 Title |  Author2  |  Editor1   | 8000-9003 |

| author_id |  fn    |    ln    |
---------------------------------
|       1   | name1  |  lname1  |
|       2   | name2  |  lname2  |
|       3   | name3  |  lname3  |

and here is my code:

SELECT author.author_id, author.fn, author.ln, COUNT(DISTINCT book.editor_id) as num
FROM `editor`, `book`
GROUP BY `editor_id`
LIMIT 0,1

but off-course i don't get what I want. The output must be:

| author_id |  fn    |    ln    |
---------------------------------
|       1   | name1  |  lname1  |

since the "author_id = 1" has 2 entries on books.

Answer 1

Try this one but please take note that I converted the author_id from varchar to int ):

SELECT book_count,a.author_id,a.fn, a.ln 
FROM author a
JOIN
(
  SELECT c.author_id,COUNT(*) book_count FROM book c
  GROUP BY c.author_id
) b 
ON a.author_id = b.author_id
ORDER BY book_count DESC LIMIT 1

Here's the SQLFiddle .