增強當前的SQLite查詢

Question

我繼承了舊的SQLite數據庫，我不應該改變（這是一個要求）。有很多的表，但我會集中在兩個：

songs 
---------- 
song_id (primary autoincrement) 
group_id (external) 
title 
audio_file_path 
wasPurchased (boolean, 0/1) 

groups 
---------- 
group_id (primary autoincrement, related to songs group_id) 
group_name 

目前，該應用程序需要執行這個查詢：

SELECT song_id,title,audio_file_path,wasPurchased,G.group_name AS groupName, 
G.group_id AS groupId FROM songs AS S JOIN groups AS G ON S.group_id=G.group_id 
ORDER BY groupName DESC 

有什麼辦法，用相同的查詢，提取有多少不同的G.group_id已被購買= 0？

任何幫助表示讚賞。

Answer 1

SELECT song_id,title,audio_file_path,wasPurchased, 
G.group_name AS groupName, G.group_id AS groupId, 
SUM (SELECT DISTINCT g.group_id 
     FROM yourtables/JOIN 
     WHERE wasPurchased = 0) as nb 
FROM songs AS S 
JOIN groups AS G ON S.group_id=G.group_id 
ORDER BY groupName DESC 

不知道這是最好的方式（從來沒有試過一個選擇的總和，但...），但我認爲這會幫助你。