如果前一列值不为空，则更新表中的下一列

Question

When a person receives a score, an entry is added into the table @uniqueScores :

Pid | Date | Score

I have a stored procedure returning a table @people with the score columns containing the data from @uniqueScores (that fall within the past 3 months)

Pid | S1 | S2 | S3 | S4 | S5

I have a small test dataset, however I'm having trouble getting any scores beyond the first score registered to a user to appear in Score2 or beyond.

Here is my test dataset

Pid | Date       | Score
 #1 | 2020/07/01 | 8
 #1 | 2020/09/15 | 8
 #2 | 2020/09/21 | 3
 #3 | 2020/10/01 | 5
 #4 | 2020/10/18 | 6
 #4 | 2020/10/31 | 2

My update statement, to update the Person column with the data

BEGIN
  UPDATE @people
  SET    [Score5] = (CASE WHEN ( [p].[Score4] is not null and [p].[Score5] is null ) THEN [us].[Score] ELSE NULL END)
         ,[Score4] = (CASE WHEN ( [p].[Score3] is not null and [p].[Score4] is null ) THEN [us].[Score] ELSE NULL END)
         ,[Score3] = (CASE WHEN ( [p].[Score2] is not null and [p].[Score3] is null ) THEN [us].[Score] ELSE NULL END)
         ,[Score2] = (CASE WHEN ( [p].[Score1] is not null and [p].[Score2] is null ) THEN [us].[Score] ELSE NULL END)
         ,[Score1] = (CASE WHEN ( [p].[Score1] is null ) THEN [us].[Score] ELSE NULL END)
  FROM   @people [p] inner join  @uniqueScores [us]
         on [p].[PersonID] = [us].[PersonID]
  WHERE  [Date] >= @DateLimit -- within the previous 3 months
END

However, the query isn't updating the table with any but the first eligible values. The returned table looks like this

Pid | S1 | S2   | S3   | S4   | S5
#1  | 8  | null | null | null | null
#2  | 3  | null | null | null | null
#3  | 5  | null | null | null | null
#4  | 6  | null | null | null | null

The first table entry which is ineligible to be considered for the table isn't included which is great, however Person #4's second score is also missing.

I've been looking at PIVOT , WHILE and a CURSOR but I've got no closer to making this work. I'm sure I've missed something simple however I just can't see it.

Answer 1

UPDATE updates each row once . Preaggregate for multiple updates:

UPDATE p
    SET Score1 = us.score_1,
        Score2 = us.score_2,
        Score3 = us.score_3,
        Score4 = us.score_4,
        Score5 = us.score_5
    FROM @people [p] inner join
         (SELECT us.PersonID,
                 MAX(CASE WHEN seqnum = 1 THEN Score END) as score_1,
                 MAX(CASE WHEN seqnum = 2 THEN Score END) as score_2,
                 MAX(CASE WHEN seqnum = 3 THEN Score END) as score_3,
                 MAX(CASE WHEN seqnum = 4 THEN Score END) as score_4,
                 MAX(CASE WHEN seqnum = 5 THEN Score END) as score_5
          FROM (SELECT us.*,
                       ROW_NUMBER() OVER (PARTITION BY PersonId ORDER BY Date) as seqnum
                FROM @uniqueScores us
                WHERE [Date] >= @DateLimit -- within the previous 3 months
               ) us
          GROUP BY us.PersonID
         ) s
         ON us.PersonID = p.PersonId;

Note: You don't specify what order you want the scores in. This puts the oldest ones first. Use ORDER BY DESC if you want the newer ones first.