SQL：控制多少記錄獲取返回2部分

Question

這是一個後續行動，我提出here的問題。如果有'genre.name ='經典電影'和'star.name = Humphrey Bogart'等限制，我該如何確保我能夠收回10部電影。要清楚，查詢必須返回10部電影的數據，而不管過濾限制是什麼。

SELECT movie.id, movie.title, star.name, star.name_url, dir.name, 
     dir.name_url, genre.name, genre.name_url 
FROM 
     (SELECT * FROM movie WHERE movie.id > 0 ORDER BY movie.id LIMIT 10) movie 
     LEFT JOIN actor 
      ON (movie.id = actor.movie_id) 
     LEFT JOIN person AS star 
      ON (actor.person_id = star.id) 
     LEFT JOIN director 
      ON (movie.id = director.movie_id) 
     LEFT JOIN person AS dir 
      ON (director.person_id = dir.id) 
     LEFT JOIN genre_classification 
      ON (movie.id = genre_classification.movie_id) 
     LEFT JOIN genre 
      ON (genre_classification.genre_id = genre.id) 

Answer 1

的問題是你從數據庫中選擇的10部電影名單與本次選擇：

(SELECT * FROM movie WHERE movie.id > 0 ORDER BY movie.id LIMIT 10) movie 

如果你想篩選下來的是列表的詳細使用WHERE子句在這個子選擇外，你可能會得到小於那10行，因爲不是所有的10個都可以符合你的標準。你可以添加新的標準子選擇像這樣：

(SELECT * FROM movie m INNER JOIN genre_classification g on g.movie_id = m.id and g.name = 'Classic Movies' WHERE m.id > 0 ORDER BY m.id LIMIT 10) movie 

這將做同樣的事情，但只有給你（最多）10部電影誰了「經典電影」的匹配類型。

這當然會，還是返回超過10行，因爲你JOIN荷蘭國際集團在演員，導演，其他流派，等你應該，但是，有多達結果集中的十個不同的電影的ID。

完整的查詢：

SELECT movie.id, movie.title, star.name, star.name_url, dir.name, 
     dir.name_url, genre.name, genre.name_url 
FROM 
     (SELECT * FROM movie m INNER JOIN genre_classification g on g.movie_id = m.id and g.name = 'Classic Movies' WHERE m.id > 0 ORDER BY m.id LIMIT 10) movie 
     LEFT JOIN actor 
      ON (movie.id = actor.movie_id) 
     LEFT JOIN person AS star 
      ON (actor.person_id = star.id) 
     LEFT JOIN director 
      ON (movie.id = director.movie_id) 
     LEFT JOIN person AS dir 
      ON (director.person_id = dir.id) 
     LEFT JOIN genre_classification 
      ON (movie.id = genre_classification.movie_id) 
     LEFT JOIN genre 
      ON (genre_classification.genre_id = genre.id)