Question

首先，问题的一般描述：我正在运行一个更新表中总数的定期过程。问题是，每次执行过程都可能需要多次更新，每次执行都取决于之前的结果。

我的问题是，可以在单个SQL Server SP中完成吗？

我的代码（我将其改为简单的样本）：

INSERT INTO CustomerMinuteSessions(time, customer, sessions, bytes, previousTotalSessions)
SELECT MS.time,
           MS.customer,
           MS.totalSessions,
           MS.totalBytes,
           CTS.previousTotalSessions
FROM (SELECT time, customer, SUM(sessions) as totalSessions, SUM(bytes) AS totalBytes
      FROM MinuteSessions
      WHERE time > @time
      GROUP BY time, x) MS
CROSS APPLY TVF_GetPreviousCustomerTotalSessions(MS.customer) CTS
ORDER BY time

previousTotalSessions列取决于UpdatedTable中的其他行，其值由CROSS APPLY TVF_GetPreviousCustomerTotalSessions检索，但如果我按原样执行SP，则全部行使用函数检索的值，而不执行执行SP期间添加的行。

为了完整起见，这里是TVF_GetPreviousCustomerTotalSessions：

FUNCTION [dbo].[TVF_GetCustomerCurrentSessions] ( @customerId int ) RETURNS @result TABLE (PreviousNumberOfSessions int) AS BEGIN INSERT INTO @result SELECT TOP 1 (PreviousNumberOfSessions + Opened - Closed) AS PreviousNumberOfSessions FROM CustomerMinuteSessions WHERE CustomerId = @customerId ORDER BY time DESC IF @@rowcount = 0 INSERT INTO @result(PreviousNumberOfSessions) VALUES(0) RETURN END

对于后续行，查询中的前一行是最好的（即没有for循环，我猜...）？

Answer 1

如果您使用的是SQL-2005及更高版本，则可以一次性使用少量CTE。如果使用SQL-2000，则可以使用内联表值函数。

我个人更喜欢CTE方法，因此我将代码的原理图转换为CTE语法。（请记住，我没有准备一套测试装置来检查它。）

WITH LastSessionByCustomer AS  
(
    SELECT CustomerID, MAX(Time)
    FROM CustomerMinuteSessions
    GROUP BY CustomerID
)
, GetPreviousCustomerTotalSessions AS
(
    SELECT LastSession.CustomerID, LastSession.PreviousNumberOfSessions + LastSession.Opened - LastSession.Closed AS PreviousNumberOfSessions
    FROM CustomerMinuteSessions LastSession
    INNER JOIN LastSessionByCustomer ON LastSessionByCustomer.CustomerID = LastSession.CustomerID
)
, MS AS
(
    SELECT time, customer, SUM(sessions) as totalSessions, SUM(bytes) AS totalBytes
    FROM MinuteSessions
    WHERE time > @time
    GROUP BY time, x
)
INSERT INTO CustomerMinuteSessions(time, customer, sessions, bytes, previousTotalSessions)
SELECT MS.time,
           MS.customer,
           MS.totalSessions,
           MS.totalBytes,
           ISNULL(GetPreviousCustomerTotalSessions.previousTotalSessions, 0)
FROM MS 
RIGHT JOIN GetPreviousCustomerTotalSessions ON MS.Customer = GetPreviousCustomerTotalSessions.CustomerID

稍微超出您的问题，我认为一旦表CustomerMinuteSessions数据库增长，您的带有交叉应用的查询可能会对数据库造成很大的损害我会添加一个索引，以提高你获得Index-Seek的机会：

CREATE INDEX IX_CustomerMinuteSessions_CustomerId
    ON CustomerMinuteSessions (CustomerId, [time] DESC, PreviousNumberOfSessions, Opened, Closed );

对select RESULT中的每一行执行INSERT

1 个答案: