如果在sql中存在列值

Question

如果[@myTable] .MessageId，我想从下面的查询中选择所有记录 在连接中将值视为0，不存在。

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



    INSERT  INTO @myTable
            ( MessageId ,
              RecieverId

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

SELECT  COUNT(CM_MessageStatus.MessageID) AS MessageID ,
        dbo.CM_MessageStatus.ReceiverID
FROM    dbo.CM_MessageStatus
        LEFT   JOIN @myTable ON [@myTable].RecieverId = CM_MessageStatus.ReceiverID
                                AND CM_MessageStatus.MessageID > [@myTable].MessageId
WHERE   --DeliveredDate IS NULL AND

- 如果[@myTable] .MessageId不存在，则将其视为0

    CM_MessageStatus.MessageID > [@myTable].MessageId
    AND ReceiverID IN ( SELECT  *
                        FROM    string_split(@UserID, ',') )
GROUP BY dbo.CM_MessageStatus.ReceiverID

注意：我想检查[@myTable] .MessageId是否不存在，考虑是否为0

Answer 1

        INSERT  INTO @myTable
        ( MessageId ,
          RecieverId

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

     IF @@ROWCOUNT= 0 
         insert into @myTable values(0,0)
         select * from @mytable
     ELSE 
         select * from @myTable