有两个相同的值时，SQL UPDATE SET一列等于0.000

Question

So here is the problem i'm trying to update column distance, first to sum the distance for each ownerID and after when there is a record with the same id address the first record should memories thee distance and the second should be 0.000

This is the expected result

So far I did the first part that calculates the distance using this code

UPDATE Action_Distance
SET [distance]=(SELECT sum([distance])
               FROM Action a2
               WHERE [name]='travel' and a2.ownerID = Action_Distance.ownerId 
               )

               WHERE [name]='drive_through' 

I don't understand how it should be done.

Answer 1

Assuming that id_action is unique for each row, then CASE expression together with a NOT EXIST subquery can be used in this way:

UPDATE Action_Distance A
SET [distance] = CASE
                    WHEN NOT EXISTS (SELECT 'anything' 
                                     FROM Action_Distance B
                                     WHERE B.[name] = 'drive_through' 
                                       AND a.ownerId = b.ownerId
                                       AND a.id_action > b.id_action)
                       THEN (SELECT SUM([distance])
                             FROM Action a2
                             WHERE [name] = 'travel' 
                               AND a2.ownerID = a.ownerId)
                       ELSE 0
                 END
WHERE 
    [name] = 'drive_through'