Sql 从类别中选择上周的前5名

我在MS SQL中有两个表：

Category
 - Id (int)

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

因此，每个类别可以有零个或多个类别元素。CategoryElement中的时间表示创建category元素的时间

我需要一些帮助来编写以下查询：order categories按过去7天中添加的类别元素数降序，并显示类别id和添加的元素数

到目前为止，我成功地编写了他们的查询，而没有在过去7天中添加以下内容：

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

---

看看下面的例子：

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

---

看看下面的例子：

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

您可以使用DATEDIFF和WHERE子句仅获取过去一周的数据，并使用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

我上面的回答假设使用SQL Server。根据您的数据库类型，代码可能会有一些变化。例如，对于MySQL，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

您可以使用DATEDIFF和WHERE子句仅获取过去一周的数据，并使用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

我上面的回答假设使用SQL Server。根据您的数据库类型，代码可能会有一些变化。例如，对于MySQL，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

---

不确定您正在使用什么RDBMS，但在SQL Server中，您可以执行以下操作：

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

---

不确定您正在使用什么RDBMS，但在SQL Server中，您可以执行以下操作：

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

---

你最后7天的约束将进入你内在连接的子查询。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

---

你最后7天的约束将进入你内在连接的子查询。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

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

演示

如果你需要前五名的话

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

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

演示

如果你需要前五名的话

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

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您正在使用什么RDBMS？数据处理功能也会随之变化。您使用的是什么关系数据库？日期处理函数也会相应地变化。我认为DATEDIFF中的参数是向后的。它们很好理解。DATEDIFF定义为DATEDIFF datepart、startdate、enddate。我已经对我的答案做了必要的修改。谢谢你的回答。然而，它并没有给出正确的结果。最后的计数应该只包含上周添加的元素数…根据问题的标题，查询只返回5个结果。我认为DATEDIFF中的参数是反向的。它们是，很好的捕获。DATEDIFF定义为DATEDIFF datepart、startdate、enddate。我已经对我的答案做了必要的修改。谢谢你的回答。然而，它并没有给出正确的结果。最终计数应仅包含上周添加的元素数…根据问题的标题，查询仅返回5个结果。