使用count sql函數在特定時間內過濾項目

Question

我想在特定時間範圍內過濾出售的文件，但我仍然不知道如何在訂購論文時插入日期。請參閱現行規範

SELECT p.PaperID, p.PaperName,COUNT(Orders.OrderID) AS NumberOfOrders FROM Orders 
LEFT JOIN Papers as p 
ON Orders.PaperID=p.PaperID 
GROUP BY PaperName, p.PaperID 

Cuurent輸出：

PaperID   PaperName   No. of Orders 
1     Paper1    2 
2     Paper2    1 

數據庫表 銷售

SaleID    OrderID   Amount    Date 
1     1     10     2013-11-10 
2     2     10     2013-11-20 
3     3     30     2013-11-30 

訂單

OrderID   PaperID 
1     1 
2     1 
3     2 

Answer 1

試試這個：

SELECT p.PaperID, p.PaperName,COUNT(Orders.OrderID) AS NumberOfOrders FROM Orders 
LEFT JOIN Papers as p ON Orders.PaperID=p.PaperID 
LEFT JOIN Sales s ON s.orderid = orders.orderid 
Where s.Date Between '2013-11-10' AND '2013-11-20' 
GROUP BY PaperName, p.PaperID 

Answer 2

在查詢中添加另一個JOIN到Sales表。現在你有Sales.Date列，您可以在WHERE子句中使用它按日期過濾：

SELECT 
    p.PaperID, p.PaperName, COUNT(Orders.OrderID) AS NumberOfOrders 
    FROM Orders AS o 
LEFT JOIN Papers AS p ON o.PaperID = p.PaperID 
LEFT JOIN Sales AS s ON o.OrderID = s.OrderID 
WHERE s.Date BETWEEN '2013-1-1' AND '2013-12-31' 
GROUP BY PaperName, p.PaperID 

作爲選擇對象不JOIN（檢查什麼在你的情況下，具有最佳性能）：

SELECT 
    p.PaperID, p.PaperName, COUNT(Orders.OrderID) AS NumberOfOrders 
    FROM Orders AS o 
LEFT JOIN Papers AS p ON o.PaperID = p.PaperID 
WHERE p.OrderID IN (
    SELECT OrderID FROM Sales WHERE Date BETWEEN '2013-1-1' AND '2013-12-31' 
) 
GROUP BY PaperName, p.PaperID