Question

I need to update some records here are the table structures

Table A is the main one we need to update some records
A(Id,DataYear0,DataYear1,DataYear3)

Table B has some other than data that we require
B(Id,Year,DataYear)

Example data for Table B:
B(abc,1950,1.25)
B(abc,1951,1.29)
..
..
B(abc,2008,1.67)
B(abc,2009,1.23)
B(abc,2010,1.52)
B(abc,2011,1.78)
B(abc,2012,NULL)

With 2012 as the current Year, I need to update the data values of the previous three years(i.e, 2011,2010,2009) in Table A

So, table A needs to be updated as A(abc,1.78,1.52,1.23) for the above example. Similarly other records need to be updated.

Id is the primary key on both tables.

The query I have so far is

UPDATE A SET
    DataYear0 = CASE WHEN Year+1 = YEAR(GETDATE()) THEN DataYear END,
    DataYear1 = CASE WHEN Year+2 = YEAR(GETDATE()) THEN DataYear END,
    DataYear2 = CASE WHEN Year+3 = YEAR(GETDATE()) THEN DataYear END
FROM A
LEFT JOIN B
    ON A.Id=B.Id

This did not work, because I think it is returning extra year records apart from the years that we want i.e., just the last three years

UPDATE A SET
   DataYear0 = CASE WHEN Year+1 = YEAR(GETDATE()) THEN DataYear END,
   DataYear1 = CASE WHEN Year+2 = YEAR(GETDATE()) THEN DataYear END,
DataYear2 = CASE WHEN Year+3 = YEAR(GETDATE()) THEN DataYear END
FROM A
LEFT JOIN B
    ON A.Id=B.Id
GROUP BY Id,Year,DataYear
HAVING ((YEAR(GETDATE())-3) <= Year) AND (Year <> YEAR(GETDATE()))

But still the data is not being updated.

Tried using CTE

;WITH cte AS
(
 SELECT 
    A.Id
    ,B.Year
    ,B.DataYear 
    ,ROW_NUMBER() OVER (PARTITION BY Id ORDER BY Year DESC) as row
 FROM A
 LEFT JOIN B
    ON A.Id=B.Id
 GROUP BY Id,Year,DataYear
 HAVING ((YEAR(GETDATE())-3) <= Year) AND (Year <> YEAR(GETDATE()))
 )


UPDATE
    A.DataYear0 = CASE WHEN row=1 THEN DataYear END
    ,A.DataYear1 = CASE WHEN row=2 THEN DataYear END
    ,A.DataYear2 = CASE WHEN row=3 THEN DataYear END
FROM A
LEFT JOIN cte
    ON A.Id = cte.Id

The data is still not updated. I would appreciate any suggestions that anyone might have. Many thanks in advance.

Answer 1

You could do something like this:

UPDATE a
    SET DataYear0 = COALESCE(d0.DataYear,DataYear0),
        DataYear1 = COALESCE(d1.DataYear,DataYear1),
        DataYear2 = COALESCE(d2.DataYear,DataYear2)
FROM A a
LEFT JOIN B d0 ON d0.Id = a.Id and d0.[Year] = YEAR(GETDATE())-1
LEFT JOIN B d1 ON d1.Id = a.Id and d1.[Year] = YEAR(GETDATE())-2
LEFT JOIN B d2 ON d2.Id = a.Id and d2.[Year] = YEAR(GETDATE())-3