Question

I need help to do this:

TABLE POSITION
ID, int (PK)
SN, varchar(10)
Lat, double
Lon, double
etc...

TABLE ACTUAL_POSITION
SN, varchar(10) (PK)
Lat, double
Lon, double

When records are inserted in the first table, corresponding (by SN) record should be updated in the second table. If no SN record is found in that table, it should be created.

Multiple records are inserted in the first table at the same time, even for the same SN, so I need to extract the very last Lat and Lon for every single SN (when vehicles are out of connection range they buffer the data to send and then send it all togheter, so the receiving sw writes into sql in a single pass) from the inserted table.

Answer 1

CREATE TRIGGER dbo.SummarizePosition
ON dbo.Position
FOR INSERT
AS
BEGIN
    ;WITH x AS 
    (
      SELECT SN, Lat, Long, 
        rn = ROW_NUMBER() OVER (PARTITION BY SN 
        ORDER BY ID DESC) -- or by timestamp col desc
      FROM inserted
      WHERE EXISTS
      ( SELECT 1 FROM dbo.Actual_Position AS p
        WHERE p.SN = inserted.SN
      )
    )
    UPDATE p
      SET p.Lat = x.Lat,
      p.Lon = x.Lon
      FROM dbo.Actual_Position AS p
      INNER JOIN x ON x.sn = p.sn
      WHERE x.rn = 1;

    ;WITH x AS 
    (
      SELECT SN, Lat, Long, /* other cols, */
       rn = ROW_NUMBER() OVER (PARTITION BY SN 
       ORDER BY ID DESC) -- or by timestamp col desc
      FROM inserted
      WHERE NOT EXISTS
      ( SELECT 1 FROM dbo.Actual_Position AS p
        WHERE p.SN = inserted.SN
      )
    )
    INSERT dbo.Actual_Position(SN, Lat, Long /*, other cols */)
      SELECT SN, Lat, Lon /*, other cols */
       FROM x
       WHERE rn = 1;
END
GO