如何使用SQL

Question

我掙扎編寫以下情形的SQL查詢創建一個從表中的矩陣型結果和任何指針將不勝感激：

我已經存儲了這樣的我的數據：

 
Zone Name | SessionId 
Zone 1 | 1 
Zone 2 | 1 
Zone 3 | 1 
Zone 1 | 1 
Zone 1 | 2 
Zone 2 | 2 
Zone 2 | 3 
Zone 3 | 3 
Zone 2 | 3 

（注意，人們可以在會話中不止一次進入同一區域）

我想產生一個輸出，顯示誰，已進入一個區域的人的百分比，也進入了另一個（即66％進入1區的人也進入2區）：

 
     Zone 1 | Zone 2 | Zone 3 
Zone 1 100% | 66% | 33% 
Zone 2 66% | 100% | 66% 
Zone 3 33% | 66% | 100% 

是否有一個特定的內置SQL函數來做這樣的事情？任何人都可以就如何實現這一目標提供任何建議？

感謝 湯姆

附：使用PostgreSQL

小提琴這裏：http://sqlfiddle.com/#!15/f379c/1/0

Answer 1

所以，如果你能處理應用方面的一些轉變：

DECLARE @ZoneCounts TABLE 
    (
    Zone nvarchar(max), 
    sessionId int 
    ) 

INSERT INTO @ZoneCounts 
values 
('Zone 1', 1), 
('Zone 2', 1), 
('Zone 3', 1), 
('Zone 1', 2), 
('Zone 2', 2) 

select v3.down, v3.across, convert(decimal(13,2),(CONVERT(decimal(13,2), v3.matchingSessions)/v3.sessionsVisitingDown) * 100) as percentage 
from 
(SELECT v2.down, v2.across, v2. matchingSessions, max(v2.matchingSessions) over (partition by v2.down) as sessionsVisitingDown 
FROM (select down, across, matchingSessions from 
(select lhs.Zone as down, rhs.Zone as across, count(lhs.sessionId) over (partition by lhs.Zone, rhs.Zone) as matchingSessions 
from @ZoneCounts as lhs inner join @ZoneCounts as rhs on lhs.sessionId = rhs.sessionId) AS v1 
GROUP BY down, across, matchingSessions) AS v2) 
as v3 

給你

NB - 採用MS SQL但應該轉換成

---

啊，Postgres的是不太一樣

SELECT v3.down, v3.across, cast(cast(v3.matchingSessions as decimal)/cast(v3.sessionsVisitingDown as decimal) * 100 as decimal(13,2)) AS percentage 
FROM 
(SELECT v2.down, v2.across, v2. matchingSessions, max(v2.matchingSessions) over (partition BY v2.down) AS sessionsVisitingDown 
FROM (SELECT down, across, matchingSessions FROM 
(SELECT lhs.name AS down, rhs.name AS across, count(lhs.id) over (partition BY lhs.name, rhs.name) AS matchingSessions 
FROM ItemList AS lhs INNER JOIN ItemList AS rhs ON lhs.id = rhs.id) AS v1 
GROUP BY down, across, matchingSessions) AS v2) 
AS v3 

這裏有一個SQL小提琴：http://sqlfiddle.com/#!15/f379c/13/0使用PostgreSQL