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如何避免子查询上的聚合错误?[复制品]

ssms sql-server

0

Yanayaya · 技术社区 · 7 年前

我有三张桌子:

Measurements (MeasureID, Time, Distance, Value)
Events(EventID, Time Value)
EventValues (EventDataID, EventID, Type, Value)

我需要获取每一个度量值、最近的事件(在过去)及其关联的事件值数据。

我现在的问题很难看:

SELECT 
    M.*,
    (SELECT TOP 1 EV.value FROM [Event] E JOIN EventValues EV ON E.EventID = EV.EventID 
     WHERE M.Time >= E.Time ORDER BY M.Time-E.Time) AS Data,
FROM [Measure] M 
ORDER BY M.Distance

它只允许我从 EventValues 桌子(我需要更多)

有什么办法可以使用连接吗?

编辑 :我还需要从度量表中选择所有条目,即使它们在第一个事件之前(即,只为联接选择空数据)

0 回复 | 直到 14 年前

1

GilM 14 年前

可以使用交叉应用程序。

SELECT  
    M.*, Data.* 
FROM [Measure] M 
CROSS APPLY
     (SELECT TOP 1 EV.* FROM [Event] E JOIN EventValues EV ON E.EventID = EV.EventID  
     WHERE M.Time >= E.Time ORDER BY E.Time DESC) AS Data
ORDER BY M.Distance

2

1

amit_g 14 年前

试试这样的(未测试)

SELECT * FROM
(
    SELECT M.*, E.*, EV.EventDataID, EV.Type, EV.Value,
        Rank() over (Partition BY M.MeasureID order by M.Time - E.Time) as Rank
    FROM [Measure] M 
    INNER JOIN [Event] E ON M.Time >= E.Time
    INNER JOIN EventValues EV ON E.EventID = EV.EventID
) T
WHERE Rank = 1

编辑

SELECT * FROM
(
    SELECT M.*, E.*, EV.EventDataID, EV.Type, EV.Value,
        Rank() over (Partition BY M.MeasureID order by M.Time - E.Time) as Rank
    FROM [Measure] M 
    LEFT JOIN [Event] E ON M.Time >= E.Time
    LEFT JOIN EventValues EV ON E.EventID = EV.EventID
) T
WHERE Rank = 1