sql - 创建一个新的计算列

Question

我知道这会很容易，但我不记得该怎么做，我有查询请参阅下面我想添加一个名为 Total Capacity 的新列，这是我的 datediff 结果 * 我的 Capcity。但是对于我的生活，我无法弄清楚。你能帮我吗？

SELECT
  Capacity.StartDate
  ,Capacity.EndDate, DATEDIFF(d,Capacity.StartDate
  ,Capacity.EndDate)+1 AS DaysOpen
  ,Capacity.Capacity
  ,Capacity.Site_Skey
FROM
  Capacity

结果

  StartDate   EndDate       DaysOpen   Capacity TotalCapacity
  01/05/2010  30/09/2010    153        46       7038

Answer 1

您可以轻松地将这两列添加到表中 - 作为计算的持久列。然后，您将可以轻松选择它们 - 它们是表中的新列，您可以像选择其他列一样选择它们 - 如果需要，您甚至可以在它们上放置索引！

ALTER TABLE [dbo].[Capacity]
    ADD DaysOpen AS DATEDIFF(d, StartDate, EndDate) PERSISTED

ALTER TABLE [dbo].[Capacity]
    ADD TotalCapacity AS DATEDIFF(d, StartDate, EndDate) * [Capacity] PERSISTED

现在您可以发出：

SELECT
    StartDate, EndDate,
    DaysOpen,
    Capacity,
    TotalCapacity
FROM
    Capacity

更新：如果您想使用该DATEDIFF+1方法 - 使用这些列规范：

ALTER TABLE [dbo].[Capacity]
    ADD DaysOpen AS (DATEDIFF(d, StartDate, EndDate) + 1) PERSISTED

ALTER TABLE [dbo].[Capacity]
    ADD TotalCapacity AS (DATEDIFF(d, StartDate, EndDate) + 1) * [Capacity] PERSISTED

Answer 2

SELECT
  Capacity.StartDate
  ,Capacity.EndDate
  ,DATEDIFF(d,Capacity.StartDate ,Capacity.EndDate)+1 AS DaysOpen
  ,Capacity.Capacity
  ,(DATEDIFF(d,Capacity.StartDate ,Capacity.EndDate)+1) * Capacity.Capcity as TotalCapacity
  ,Capacity.Site_Skey
FROM
  Capacity

Answer 3

像这样的东西？

SELECT
  Capacity.StartDate
  ,Capacity.EndDate
  ,DATEDIFF(d, Capacity.StartDate, Capacity.EndDate) + 1 AS DaysOpen
  ,Capacity.Capacity
  ,(DATEDIFF(d, Capacity.StartDate, Capacity.EndDate) + 1) * Capacity.Capacity AS TotalCapacity
FROM
  Capacity

Answer 4

SELECT
  Capacity.StartDate
  ,Capacity.EndDate
  ,DATEDIFF(d,Capacity.StartDate
  ,Capacity.EndDate)+1 AS DaysOpen
  ,Capacity.Capacity
  ,Capacity.Site_Skey
  ,(DATEDIFF(d,Capacity.StartDate
  ,Capacity.EndDate)+1 ) * Capacity.Capacity
FROM
  Capacity