SELECT
   c.id,
   c.CategoryName,
   c.Description,
   (SELECT count(t.id)
    FROM topic t
    WHERE t.categoryId = c.id) AS NumberOfTopics,
   (SELECT count(p.id)
    FROM post p
    JOIN topic t ON p.topicId = t.id
    WHERE t.categoryId = c.id) AS NumberOfPosts,
   (SELECT top 1 max(p.createdOn)
    FROM post p
    JOIN topic t ON p.topicId = t.id
    WHERE t.categoryId = c.id) AS LastPostDate,
   (SELECT top 1 createdby
    FROM post p
    JOIN topic t ON p.topicId = t.id
    WHERE t.categoryId = c.id
    ORDER BY p.createdon DESC) AS byperson
FROM
   category c;