SQL计算计数大于列值

Question

I have table in which deleieverddate are saved, some of the delivered date are null and some of them are not I want to calculate the count for which delievered date is null and skip the delieverd date of those who are missed in between.

ie

deleievered date

NULL
NULL
NULL

count should be 3.

ie

NULL
NULL
9/22/2017
NULL
10/22/2017
NULL

Count should be 1 here skip all previous where deievered date is not null

I have tried this but it is too costly.

DECLARE @myTable TABLE
    (
      MessageId BIGINT ,
      ReceiverID VARCHAR(100)
    )

DECLARE @mySecondTable TABLE
    (
      MessageId BIGINT ,
      ReceiverID VARCHAR(100),
      DeliveredDate DATETIME
    )


DECLARE @myLastTable TABLE
    (
      MessageId BIGINT ,
      ReceiverID VARCHAR(100)
    )





INSERT  INTO @myTable
        ( MessageId ,
          ReceiverID

        )
        SELECT  MAX(MessageID) ,
                ReceiverID
        FROM    dbo.CM_MessageStatus
        WHERE   ReceiverID IN ( SELECT  *
                                FROM    string_split(@UserID, ',') )
                AND DeliveredDate IS NOT NULL
        GROUP BY ReceiverID






INSERT  INTO @mySecondTable
        ( MessageId ,
          ReceiverID,
          DeliveredDate

        )

SELECT  CM_MessageStatus.MessageID,
        dbo.CM_MessageStatus.ReceiverID,
        DeliveredDate
FROM    dbo.CM_MessageStatus
WHERE   DeliveredDate IS NULL AND

         ReceiverID IN ( SELECT  *
                            FROM    string_split(@UserID, ',') )
--GROUP BY dbo.CM_MessageStatus.ReceiverID,DeliveredDate




--Now check each userid
declare @ReceiverID NVARCHAR(MAX)
while exists (select * from @mySecondTable)
BEGIN

            select top 1 @ReceiverID = ReceiverID
            from @mySecondTable
            order by ReceiverID ASC 





        IF EXISTS( SELECT * FROM @myTable WHERE ReceiverID=@ReceiverID)
        BEGIN
                            INSERT  INTO @myLastTable
                                    ( MessageId ,
                                      ReceiverID

                                    )


                                    SELECT  MessageID,
                                            @ReceiverID
                                    FROM    @mySecondTable
                                    WHERE   DeliveredDate IS NULL
                                            AND MessageId > ( SELECT
                                                      MessageId
                                                      FROM
                                                      @myTable
                                                      WHERE
                                                      ReceiverID = @ReceiverID
                                                      )
                                                      AND ReceiverID=@ReceiverID
                                                      --GROUP BY ReceiverID
        END


        ELSE
        BEGIN
                INSERT  INTO @myLastTable
                                    ( MessageId ,
                                      ReceiverID

                                    )
                                   SELECT  MessageID ,
                                            ReceiverID
                                    FROM    @mySecondTable
                                    WHERE   DeliveredDate IS NULL
                                    AND ReceiverID=@ReceiverID
        END   


        delete @mySecondTable
        where ReceiverID = @ReceiverID
END 

    SELECT COUNT(MessageId) AS MessageId,ReceiverID FROM @myLastTable
    GROUP BY ReceiverID

It took 35 seconds for 8 hundred thousand which is too costly, how can I do this in one select. Efforts are share in the question.

Answer 1

Well, you have to have some order to the data. That is, an ID column, or something that represents when a row was inserted compared to all other rows. In this example, I use MessageID. Each time a row is inserted, it gets a new MessageID which is 1 greater than the previous. Without SOME column (insert date) or a PrimaryKey / Auto Increment column this is impossible. So, if you have one, here is how you can do it.

declare @table table (MessageId  int identity(1,1), dt date)
insert into @table

values
(NULL),
(NULL),
('9/22/2017'),
(NULL),
('10/22/2017'),
(NULL)



select
    count(*)
from 
    @table
where 
    --limits rows to the last one where data is not null
    MessageID > (
    select max(MessageID)
    from @table
    where dt is not null)
or
    --if all dates are null
    (
    select max(dt)
    from @table) is null