作爲條件的聚合函數

我有問題試圖使用聚合函數結果作爲條件。基本上，我需要選擇具有行「查看次數」超過3個。這裏是代碼的工作：作爲條件的聚合函數

SELECT b.BranchNo AS "Branch Number", 
p.PropertyNo || ', ' || p.PostCode || ', ' || p.City || ', ' || p.Street AS "Object address" , count(v.ViewDate) as "View count" 
FROM Branch b INNER JOIN PropertyForRent p ON b.BranchNo=p.PropertyBranchNo 
INNER JOIN Viewing v ON p.PropertyNo=v.ViewPropertyNo WHERE v.ViewDate>='2014-01-01' 
GROUP BY b.BranchNo, p.PropertyNo;

我試圖用類似的東西：

HAVING count(v.ViewDate)>=3

但是，這顯然沒沒有工作。沒有使用子查詢來製造這種情況的方法嗎？

來源

2016-11-21 Glebzex

'但這顯然沒有工作......呃，爲什麼沒有工作？ – Lamak

正如我所知，HAVING子句必須使用GROUP BY或默認情況下使用當前表獲取組。是的，那不僅僅是執行... – Glebzex

爲什麼不能爲你工作？你在哪裏試圖把HAVING子句放在你的查詢中？ –

看起來您的select中的字段與group by不匹配，但除此之外，「基於聚合的條件」正是having子句的用途。例如，此查詢應該有效：

SELECT 
b.BranchNo AS "Branch Number", 
p.PropertyNo || ', ' || p.PostCode || ', ' || p.City || ', ' || p.Street AS "Object address" , 
count(v.ViewDate) as "View count" 
FROM Branch b INNER JOIN PropertyForRent p ON b.BranchNo=p.PropertyBranchNo 
INNER JOIN Viewing v ON p.PropertyNo=v.ViewPropertyNo WHERE v.ViewDate>='2014-01-01' 
GROUP BY b.BranchNo, p.PropertyNo, p.PostCode, p.City, p.Street 
HAVING count(v.ViewDate) >= 3;

來源

2016-11-21 20:41:34 SlimsGhost

您需要在查看錶子查詢中進行分組以獲取計數。然後加入。

SELECT b.BranchNo AS [Branch Number], 
    p.PropertyNo + ', ' + p.PostCode + ', ' + p.City + ', ' + p.Street AS [Object address], 
    v.ViewCount 

FROM Branch b 
    INNER JOIN PropertyForRent p ON b.BranchNo=p.PropertyBranchNo 
    INNER JOIN (SELECT ViewPropertyNo, COUNT(*) as ViewCount 
       FROM Viewing 
       WHERE v.ViewDate>='2014-01-01' 
       GROUP BY ViewPropertyNo 
       ) AS v ON p.PropertyNo = v.ViewPropertyNo 
WHERE v.ViewCount >= 3;

來源

2016-11-21 20:42:15 under

作爲條件的聚合函數

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