稍微復雜的 SQL 查詢

Question

編寫一個 SQL 查詢，按用戶返回文章數，結果如下，列標題為：'user_id', 'username', 'total_count_of_articles' 按文章數排序

Answer 1

這樣的事情應該返回指定的結果集：

 SELECT u.id AS user_id
      , u.user_name
      , SUM(a.user_id IS NOT NULL) AS total_count_of_articles
   FROM users u
   LEFT
   JOIN users_articles a
     ON a.user_id = u.id
  GROUP BY u.id, u.user_name
  ORDER BY total_count_of_articles DESC