Question

I have a table, SUBSCRIBERS, in which I can have more than one entry per subscriber.

(let’s say because it stopped being a subscriber and now it became a customer again, so it has a different ‘identity’ but the same ‘subno’)

I need an UPDATE statement that updates a column in a row (let’s say their address), but only for the latest record for that subscriber (with the latest EffectiveDate).

So I figured out how to select such a row:

SELECT 
    t1.identity, t1.Subno, t1.EffectiveDate
FROM 
    SUBSCRIBERS t1
INNER JOIN 
    (SELECT subno,max(EffectiveDate) as LatestDate 
     FROM SUBSCRIBERS
     GROUP BY Subno) t2 ON t1.Subno = t2.Subno AND t1.EffectiveDate = t2.LatestDate

But I don’t know how to UPDATE the row for a given subno value. Well, I do, but I don’t want to do it with 17 nested select statements.

Thanks!

Answer 1

You can use ‘Update from’ :

UPDATE SUBSCRIBERS 
SET Address = 'the address' 
FROM SUBSCRIBERS t1
INNER JOIN 
  (SELECT subno,max(EffectiveDate) as LatestDate FROM SUBSCRIBERS
   GROUP BY Subno) t2 
ON t1.Subno = t2.Subno and t1.EffectiveDate = t2.LatestDate