Question

我在MS SQL中有两个表：

Category
 - Id (int)

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

因此，每个类别可以包含零个或多个类别元素。 Time，在CategoryElement中，表示创建类别元素的时间。

我需要一些帮助来编写以下查询：订单类别按照过去7天内添加的类别元素的数量减少，并显示类别ID和添加的元素数量。

到目前为止，我设法写了他们的查询而没有“在过去7天内添加”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

Answer 1

您可以使用DATEDIFF和WHERE子句获取上周，TOP 5将结果限制为仅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

我上面的回答假定使用SQL Server。根据您的数据库类型，代码可能会稍有变化。例如，对于MySQL，它将如下所示：

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

Answer 2

看看像：

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

Answer 3

不确定您使用的是哪种RDBMS，但在SQL Server中可以这样做：

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

Answer 4

你的“最后7天”克制会进入你内心加入的子查询中。像这样。

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

Answer 5

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

Answer 6

您可以尝试此查询

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

SQLFiddle上的演示

如果你需要TOP 5那么

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

从类别中选择上周的前5名

6 个答案: