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在上週選擇前5我在MS SQL兩個表：從

Category 
- Id (int) 

CategoryElement 
- Id (int) 
- CategoryId (int) //References Category.Id 
- Time (datetime)

所以，每個類別可以有零組或多個類別的元素。 CategoryElement中的時間表示創建類別元素的時間。

我需要一些幫助來編寫以下查詢：按照最近7天添加的類別元素數降序排列的類別類別，並顯示類別ID以及添加了多少元素。

到目前爲止，我設法寫他們查詢沒有「在過去的7天增加了」部分：

SELECT c.Id, e.ElemCount 
FROM dbo.Categories AS c 
INNER JOIN 
    (SELECT CategoryId, COUNT(1) AS ElemCount, MAX(Time) AS LatestElem 
    FROM dbo.CategoryElements 
    GROUP BY CategoryId) AS e 
ON c.ID = e.CategoryId 
ORDER BY e.LatestElem DESC

來源

2013-03-01 user1798724

什麼是您使用RDBMS TOP？日期處理功能因此而異。 – 2013-03-01 20:38:42

MSSQL Sever 2008 – user1798724 2013-03-01 21:20:53

看是這樣的：

WHERE (Date(now()) - Date(Time)) < 7

來源

2013-03-01 20:40:59 jbh

您可以使用DATEDIFF和WHERE子句以獲得剛剛過去的一週，TOP 5將結果限制爲只有5行。

SELECT TOP 5 c.Id, e.ElemCount 
FROM dbo.Categories AS c 
INNER JOIN 
    (SELECT CategoryId, COUNT(1) AS ElemCount, MAX(Time) AS LatestElem 
    FROM dbo.CategoryElements 
    GROUP BY CategoryId) AS e 
ON c.ID = e.CategoryId 
WHERE DATEDIFF(d, e.Time, GetDate()) < 7 
ORDER BY e.LatestElem DESC

我上面的答案假定使用SQL Server。根據您的數據庫類型，代碼可能會有所變化。例如，對於MySQL的將是如下：

SELECT c.Id, e.ElemCount 
FROM dbo.Categories AS c 
INNER JOIN 
    (SELECT CategoryId, COUNT(1) AS ElemCount, MAX(Time) AS LatestElem 
    FROM dbo.CategoryElements 
    GROUP BY CategoryId) AS e 
ON c.ID = e.CategoryId 
WHERE (Date(now()) - Date(e.Time)) < 7 
ORDER BY e.LatestElem DESC 
LIMIT 5

來源

2013-03-01 20:41:12 Jeremy1026

我認爲你在'DATEDIFF'中的參數是倒退的。 – 2013-03-01 20:45:07

他們很好，趕上。 'DATEDIFF'被定義爲'DATEDIFF（datepart，startdate，enddate）'。我已經對我的回答進行了必要的修改。 – Jeremy1026 2013-03-01 20:46:28

謝謝你的回答。但是，它沒有給出正確的結果。最終計數應僅包含上週添加的元素的數量... – user1798724 2013-03-01 21:26:47

不知道你正在使用，但在SQL Server中，你可以做什麼RDBMS：

SELECT c.Id, e.ElemCount 
FROM dbo.Categories AS c 
INNER JOIN 
    (SELECT CategoryId, COUNT(1) AS ElemCount, MAX(Time) AS LatestElem 
    FROM dbo.CategoryElements 
    WHERE DATEDIFF(d, Time, CURRENT_TIMESTAMP) <= 7 
    GROUP BY CategoryId) AS e 
ON c.ID = e.CategoryId 
ORDER BY e.LatestElem DESC

來源

2013-03-01 20:41:23

你的「過去7天」的約束會進入你的內心加入的子查詢。像這樣。

SELECT CategoryId, COUNT(1) AS ElemCount, MAX(Time) AS LatestElem 
FROM dbo.CategoryElements 
WHERE Time > dateadd(dd,-7,getDate()) -- 7 Days prior to today 
GROUP BY CategoryId

來源

2013-03-01 20:42:58 cameronjchurch

select CategoryId, count(*) as cnt 
from CategoryElement 
where dateadd(day, -7, getdate())<= Time 
group by CategoryID 
order by count(*) desc

來源

2013-03-01 20:43:38 shibormot

你可以試試這個查詢上SQLFiddle

SELECT CategoryId, COUNT(*) AS numbOfCat 
FROM dbo.CategoryElement 
WHERE [Time] BETWEEN DATEADD(day, -7, GETDATE()) AND GETDATE() 
GROUP BY CategoryId 
ORDER BY MAX(Time) DESC

演示如果您需要5然後

SELECT TOP 5 CategoryId, COUNT(*) AS numbOfCat 
FROM dbo.CategoryElement 
WHERE [Time] BETWEEN DATEADD(day, -7, GETDATE()) AND GETDATE() 
GROUP BY CategoryId 
ORDER BY MAX(Time) DESC

來源

2013-03-01 22:45:47

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