Question

我有以下三个查询，它们可以获得三个特定时间段内产品的平均价格：所有数据，过去7天和过去30天。

SELECT AVG(Price) AS AggregatedPrice, COUNT(*) AS PCount
FROM dbo.Products
WHERE Id = @id

SELECT AVG(Price) AS AggregatedPrice, COUNT(*) AS PCount
FROM dbo.Products
WHERE Id = @id AND DATEDIFF(day, UpdatedDatetime, getdate()) < 7

SELECT AVG(Price) AS AggregatedPrice, COUNT(*) AS PCount
FROM dbo.Products
WHERE Id = @id AND DATEDIFF(day, UpdatedDatetime, getdate()) < 30

这三个查询给了我正确的数据，但不是我想要的形式。有没有办法将这三个查询合并为一个。我的最终目标是创建一个包含所有这些数据的视图。

此外，在我看来，7天的平均值可以在30天和所有列表中重复使用。我可以进行优化吗？

Answer 1

SELECT @Id
       , t1.AggregatedPrice AggregatedPrice_ALL, t1.PCount PCount_ALL
       , t2.AggregatedPrice AggregatedPrice_7, t2.PCount PCount_7
       , t3.AggregatedPrice AggregatedPrice_30, t3.PCount PCount_30
FROM
  (SELECT Id, AVG(Price) AS AggregatedPrice, COUNT(*) AS PCount
     FROM dbo.Products
    WHERE Id = @id) t1
  JOIN 
  (SELECT Id, AVG(Price) AS AggregatedPrice, COUNT(*) AS PCount
     FROM dbo.ApplicationPrice
    WHERE Id = @id AND DATEDIFF(day, UpdatedDatetime, getdate()) < 7) t2 
  ON t1.Id = t2.id
  JOIN
  (SELECT Id, AVG(Price) AS AggregatedPrice, COUNT(*) AS PCount
     FROM dbo.ApplicationPrice
    WHERE Id = @id AND DATEDIFF(day, UpdatedDatetime, getdate()) < 30) t3
  ON t1.Id = t3.id

Answer 2

我没有T-SQL方便测试语法，但它应该是这样的：

SELECT t1.AggregatedPrice, t1.PCount, t2.AggregatedPrice, t2.PCount, t3.AggregatedPrice, t3.PCount 
FROM
  (SELECT AVG(Price) AS AggregatedPrice, COUNT(*) AS PCount  FROM dbo.Products  WHERE Id = @id) t1,
  (SELECT AVG(Price) AS AggregatedPrice, COUNT(*) AS PCount  FROM dbo.Products  WHERE Id = @id AND DATEDIFF(day, UpdatedDatetime, getdate()) < 7) t2,
  (SELECT AVG(Price) AS AggregatedPrice, COUNT(*) AS PCount  FROM dbo.Products  WHERE Id = @id AND DATEDIFF(day, UpdatedDatetime, getdate()) < 30) t3

Answer 3

试试这个：

SELECT  AVG(Price) AS AggregatedPrice, 
        COUNT(*) AS PCount,
        AVG(CASE WHEN DATEDIFF(day, UpdatedDatetime, getdate()) < 7 THEN Price ELSE NULL END) AS AggregatedWeekPrice, 
        COUNT(CASE WHEN DATEDIFF(day, UpdatedDatetime, getdate()) < 7 THEN 1 ELSE NULL END) AS PWeekCount,
        AVG(CASE WHEN DATEDIFF(day, UpdatedDatetime, getdate()) < 30 THEN Price ELSE NULL END) AS AggregatedMonthPrice, 
        COUNT(CASE WHEN DATEDIFF(day, UpdatedDatetime, getdate()) < 30 THEN 1 ELSE NULL END) AS PMonthCount,
FROM dbo.Products
WHERE Id = @id

Answer 4

像这样的东西。确保正确测试

SELECT
      AVG(Price) AS AggregatedPrice
    , COUNT(*) AS PCount
    , AVG(CASE WHEN DATEDIFF(day, UpdatedDatetime, getdate()) < 7 THEN Price ELSE Null End) AS AggregatedPrice7Days
    , SUM(CASE WHEN DATEDIFF(day, UpdatedDatetime, getdate()) < 7 THEN 1 ELSE 0 End) AS AggregatedPrice7Days
    , AVG(CASE WHEN DATEDIFF(day, UpdatedDatetime, getdate()) < 30 THEN Price ELSE Null End) AS AggregatedPrice30Days
    , SUM(CASE WHEN DATEDIFF(day, UpdatedDatetime, getdate()) < 30 THEN 1 ELSE 0 End) AS AggregatedPrice30Days
FROM
    dbo.Products
WHERE
    Id = @id

计算三个时间段的平均值

4 个答案: