sql - 查询以查找表中不可用的所有日期

Question

我想为这个问题写一个查询：

显示 1997 年 8 月没有下订单的日子。

我可以找到下订单的天数，但是如何找到没有下订单的天数？

这显示了下订单的日期：

SELECT
   o.OrderID,
   day(o.OrderDate) AS 'Date',
   sup.CompanyName 
FROM
   Orders o 
   INNER JOIN OrderDetails od ON o.OrderID = od.OrderID 
   INNER JOIN Products p ON od.ProductID = p.ProductID 
   INNER JOIN Suppliers sup ON p.SupplierID = sup.SupplierID 
WHERE
   sup.CompanyName = 'Tokyo Traders'
   AND o.OrderDate BETWEEN '1/1/1997' AND '1/31/1997'

Answer 1

您需要一个可以加入的日期表来查找缺失的日期。

假设它的 SQL Server：

您可以加入您的查询以获取结果

WITH DatesTable
AS
(
  SELECT CAST('2007-08-01' as datetime) AS [date]
  UNION ALL
  SELECT DATEADD(dd, 1, [date])
  FROM DatesTable
  WHERE DATEADD(dd, 1, [date]) <= '2007-08-31'
)
SELECT [date] FROM DatesTable
OPTION (MAXRECURSION 0);

一些类似的东西

WITH DatesTable
AS
(
  SELECT CAST('2007-08-01' as datetime) AS [date]
  UNION ALL
  SELECT DATEADD(dd, 1, [date])
  FROM DatesTable
  WHERE DATEADD(dd, 1, [date]) <= '2007-08-31'
)
SELECT DT.[date]
FROM
   DatesTable DT 
   Left Outer Join Orders o on o.OrderDate = DT.[Date]

WHERE o.OrderDate is null

OPTION (MAXRECURSION 0);

Answer 2

执行此操作的跨数据库方法是创建一个包含每个日期的行的表，然后将其左连接到您的明细表；空值是没有匹配的地方。

Answer 3

假设 SQL Server：

WITH Dts AS (
   SELECT DateAdd(day, V.number, '19970801') Dt
   FROM master.dbo.spt_values V
   WHERE V.type = 'P'
   AND V BETWEEN 1 AND 31
)
SELECT Dts.Dt
WHERE NOT EXISTS (
   SELECT *
   FROM
      Orders o 
      INNER JOIN Suppliers sup ON p.SupplierID = sup.SupplierID 
   WHERE
      sup.CompanyName = 'Tokyo Traders'
      AND Dts.Dt = o.OrderDat
)

我在 CompanyName 上保留了您的情况，因为我认为您想要Tokyo Traders没有下订单的日子。