SQL-將結果列中的所有值相加，並使用同一查詢中的另一列計算百分比

Question

我發現很難在標題中描述我的問題，但是在這里我會更加清楚。 我有兩個表users_friends和active_users ...這是兩者的架構

CREATE TABLE `users_friends` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `user_id` int(11) DEFAULT NULL,
  `friend_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `friend_id_user_id_index` (`friend_id`,`user_id`),
  KEY `user_id` (`user_id`)
) ENGINE=InnoDB AUTO_INCREMENT=7967354 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;


CREATE TABLE `active_users` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `first` varchar(155) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
) ENGINE=InnoDB AUTO_INCREMENT=150948970 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

我想查看關注1個人，2個人，3個人等的active_users的百分比

我運行了此查詢，使我得到了跟隨X人數的用戶數

( SELECT count(t.total_follows) AS users_count, t.total_follows FROM ( ( SELECT count(*) total_follows, active_users.id FROM active_users INNER JOIN users_friends on users_friends.user_id = active_users.id GROUP BY active_users.id ) AS t ) GROUP BY t.total_follows ORDER BY t.total_follows )

這是結果

users_count   total_follows
   5                   1
   3                   2
   2                   3

我可以通過修改上面的查詢並像這樣匯總users_count來獲得users_count列的總和

select SUM(t1.users_count) as total_sum from ( < insert above query> ) as t1

但我不知道如何計算users_count列的總和除以users_count ，這將為我提供如下所示的所需結果

users_count    total_follows   percentage
   5                  1           50.0
   3                  2           30.0
   2                  3           20.0        

我知道我可以通過這樣做來獲得此列值

(count(t.total_follows) / 10) * 100 as percentage

但我無法對查詢中的總和（10）進行硬編碼。 我需要查詢才能在1次運行中計算所有內容。 如何修改查詢以實現此目的？

Answer 1

您可能想嘗試使用“ with”語句：

WITH x as
( 
SELECT count(t.total_follows) AS users_count, 
t.total_follows 
FROM ( ( SELECT count(*) total_follows, active_users.id 
FROM active_users 
INNER JOIN users_friends on users_friends.user_id = active_users.id 
GROUP BY active_users.id ) AS t ) 
GROUP BY t.total_follows 
ORDER BY t.total_follows )
)

SELECT *, COUNT/(SELECT SUM(users_count) FROM x)::FLOAT percentage from x

Answer 2

我最終只是計算所有列的總和，並將它們存儲在一個名為@total_sum的變量中，然后在第二個查詢中使用它……如果我可以使用WITH語句（如@Stoddard Meigs建議的），那會很好。我的mysql版本不支持

set @total_sum = (select SUM(t1.users_count) as total_sum from ( ( SELECT 
count(table1.total_follows) AS users_count, table1.total_follows FROM ( ( 
SELECT count(*) total_follows, active_users.id FROM active_users INNER JOIN 
users_friends on users_friends.user_id = active_users.id GROUP BY 
active_users.id ) AS table1 ) GROUP BY table1.total_follows ORDER BY 
table1.total_follows ) ) as t1);

( SELECT count(table1.total_follows) AS users_count, table1.total_follows, 
(count(table1.total_follows) / @total_sum) * 100 as percentage FROM ( ( SELECT 
count(*) total_follows, active_users.id FROM active_users INNER JOIN 
users_friends on users_friends.user_id = active_users.id GROUP BY 
active_users.id ) AS table1 ) GROUP BY table1.total_follows ORDER BY 
table1.total_follows )