2015-12-06 60 views
1

我想下面的轉換爲Rails的Ruby代碼:轉換SQL語句到Rails的ActiveRecord

SELECT * FROM ALBUMS 
WHERE TITLE='Greatest Hits' 
AND ARTIST='The Beatles'; 

SELECT COUNT(ID) FROM ALBUMS 
WHERE TITLE='Greatest Hits' 
AND ARTIST='The Beatles'; 

對於第一個,我讀過有關Ruby中採摘方法,但我不知道該怎麼採摘給予了多重限制,在這種情況下,不僅僅是標題,還包括藝術家。

對於第二個,我只想指出有多少次出現的標題和藝術家是相同的。

請幫忙? 我的最佳來源:http://apidock.com/rails/ActiveRecord/Calculations/pluck

回答

0
SELECT * FROM ALBUMS 
WHERE TITLE='Greatest Hits' 
AND ARTIST='The Beatles'; 

假設一個名爲專輯

Album.where(title: "Greatest Hits", artist: "The Beatles") 

模型對於第二

SELECT COUNT(ID) FROM ALBUMS 
WHERE TITLE='Greatest Hits' 
AND ARTIST='The Beatles'; 

使用count方法。

Album.where(title: "Greatest Hits", artist: "The Beatles").count(:id) 
+0

感謝您的回答。這裏是我的後續問題的鏈接:http://stackoverflow.com/questions/34113578/using-plucked-values-in-ruby-on-rails – Rob