MS SQL服务器延迟

Question

I'm trying to apply a condition to LAG in a SQL query. Does anyone know how to do this?

This is the query:

  SELECT CONCAT([FirstName],' ',[LastName]) AS employee,
         CAST([ArrivalTime] AS DATE) AS date,
         CAST(DATEADD(hour,2,FORMAT([ArrivalTime],'HH:mm')) AS TIME) as time,
         CASE [EventType]
         WHEN 20001 THEN 'ENTRY'
         ELSE 'EXIT'
         END AS Action,
         OutTime = 
  CASE [EventType]
  WHEN '20001'
  THEN DATEDIFF(minute,Lag([ArrivalTime],1) OVER(ORDER BY [CardHolderID], [ArrivalTime]), [ArrivalTime]) 
  ELSE
  NULL
  END
  FROM [CCFTEvent].[dbo].[ReportEvent]
  LEFT JOIN [CCFTCentral].[dbo].[Cardholder] ON  [CCFTEvent].[dbo].[ReportEvent].[CardholderID] = [CCFTCentral].[dbo].[Cardholder].[FTItemID]
  WHERE EventClass = 41
  AND [FirstName] IS NOT NULL
  AND [FirstName] LIKE 'Leeann%'

The problem I have is when the times are subtracted between two different dates, it must also be NULL when subtracting between two different dates.

The 910 is incorrect.

Answer 1

I'd add another condition to your case statement. ie

...
CASE 
   WHEN [EventType] = '20001' AND DATEDIFF(DAY,[ArrivalTime],LAG([ArrivalTime]) over (ORDER BY [CardHolderID], [ArrivalTime])) > 0
   THEN NULL
   WHEN [EventType] = '20001'
   THEN DATEDIFF(minute,Lag([ArrivalTime],1) OVER(ORDER BY [CardHolderID], [ArrivalTime]), [ArrivalTime])
   ELSE NULL

Answer 2

It seems to me that the LAG just needs to be partitioned by the date (& some other fields for good measure).

If the previous date is in another partition,
then the LAG will return NULL,
then the datediff will return NULL.

SELECT 
 CONCAT(holder.FirstName+' ', holder.LastName) AS employee,
 CAST(repev.ArrivalTime AS DATE) AS [date],
 CAST(SWITCHOFFSET(repev.ArrivalTime,'+02:00') AS TIME)  as [time],
 IIF(repev.EventType = 20001, 'ENTRY', 'EXIT') AS Action,
 (CASE WHEN repev.EventType = 20001
  THEN DATEDIFF(minute, LAG(repev.ArrivalTime) 
                        OVER (PARTITION BY repev.EventClass, repev.CardholderID, CAST(repev.ArrivalTime AS DATE) 
                              ORDER BY repev.ArrivalTime), repev.ArrivalTime)
  END) AS OutTime
FROM [CCFTEvent].[dbo].[ReportEvent] AS repev
LEFT JOIN [CCFTCentral].[dbo].[Cardholder] AS holder ON holder.FTItemID = repev.CardholderID
WHERE repev.EventClass = 41
  AND holder.FirstName LIKE 'Leeann%'

Test on db<>fiddle here