分组并计算不返回我期望的结果

我有这张表，我需要知道艺术家在他/她的职业生涯中搅动了多少张专辑，为了简洁起见，我只会发布一位艺术家。分组并计算不返回我期望的结果

"artist_ID" "song_ID" "album_ID" "touring" 
"57"  "98"  "48"  "No"   
"57"  "99"  "48"  "No"   
"57"  "100"  "48"  "Sí"   
"57"  "101"  "48"  "No"   
"57"  "102"  "48"  "No"   
"57"  "103"  "48"  "No"   
"57"  "104"  "48"  "No"   
"57"  "105"  "48"  "No"   
"57"  "106"  "48"  "No"   
"57"  "279"  "163"  "No"   
"57"  "280"  "163"  "No"   
"57"  "281"  "163"  "No"   
"57"  "380"  "241"  "No"   
"57"  "381"  "241"  "No"

然后获取数据我该走：

SELECT artist_ID, 
    count(*) AS churned_albums 
FROM relation 
GROUP BY group_ID, 
    album_ID;

我期待下面的数据：

"artist_ID" "churned_albums"   
"57"  "3"

但是，唉，我得到这个：

"artist_ID" "churned_albums" 
"57"  "9"    
"57"  "3"    
"57"  "2"

它为每张专辑的每首歌曲计数，我不知道如何告诉MySQL忽略darn歌曲并只计算专辑。我也尝试count(artist_ID)而不是count(*)和其他几个排列，但似乎没有任何工作。

这个问题与How to use count and group by at the same select statement和Using group by on multiple columns密切相关，但他们没有帮助。 :(

感谢您的帮助！:)

来源

2016-04-07 Deses

有一个在你的数据没有“GROUP_ID”一栏。 – Tibrogargan

为什么选择一件事，但由另一件事组？ – Strawberry

@Tibrogargan woops！忘了编辑这些。该表是另一种语言，我忘了翻译这些字符串。：P – Deses

算独特的专辑的＃我为你想要查询的可视化创造了sqlfiddle 。看看这里：http://sqlfiddle.com/#!9/d1372/2

我已经使用的查询：

select group_id, count(distinct album_id) AS churned_albums 
from relations 
group by group_id;

来源

2016-04-07 23:03:11 arsho

我在sqlfiddle上做了同样的查询，但是速度更快：P –

谢谢模糊和arsho！也感谢您让我知道SQL小提琴，它会派上用场，为将来的问题。 :) – Deses

您可以使用count(distinct album_id)每group_id

select group_id, 
    count(distinct album_id) as churned_albums 
from relation 
group by group_id

来源

2016-04-07 22:55:17 FuzzyTree

分组并计算不返回我期望的结果

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