Question

在下面的查询中，我想从JOIN语句中删除子查询（因为我的两个SELECT语句正在从同一个表中选择数据）。我该如何使用该别名？在此先感谢您的帮助。

declare @StartDate datetime= '8/01/2011'
declare @EndDate datetime = '9/20/2011'
declare @PortfolioId int = 6

SELECT
   Previous.PreviousNAV,
   Todays.TodaysNAV,
   ISNULL((Todays.TodaysNAV-Previous.PreviousNAV),0) NetChange,
   ISNULL((Todays.TodaysNAV-Previous.PreviousNAV) / Todays.TodaysNAV,0) BAMLIndex
FROM
(
   SELECT PortfolioId,ISNULL(NAV,0) PreviousNAV
   FROM Fireball..NAV
   WHERE Date BETWEEN @StartDate AND @EndDate and PortfolioId = @PortfolioId
) Previous
JOIN
(
   SELECT PortfolioId,ISNULL(NAV,0) TodaysNAV
   FROM Fireball..NAV
   WHERE Date = @EndDate and PortfolioId = @PortfolioId
) Todays
ON Previous.PortfolioId = Todays.PortfolioId

Answer 1

完全消除子查询。我不认为他们在查询中添加任何内容。试试这个：

SELECT
   Previous.NAV as PreviousNAV,
   Todays.NAV as TodaysNav,
   ISNULL((Todays.NAV-Previous.NAV),0) NetChange,
   ISNULL((Todays.NAV-Previous.NAV) / Todays.NAV,0) BAMLIndex
FROM
    Fireball..NAV as Previous
JOIN
    Fireball..NAV as Todays
    ON Previous.portfolioID = Todays.PortfolioID
WHERE Previous.Date BETWEEN @StartDate AND @EndDate 
    AND Previous.PortfolioId = @PortfolioId
    AND Todays.Date = @EndDate

从JOIN中删除子查询？

1 个答案: