RE: create YTD in a Table – SQLServerCentral

SSC Guru

Points: 186127

September 6, 2012 at 2:36 am

ScottPletcher (9/5/2012)
Since the table already contains the previous year's YTD totals, would a simple LEFT JOIN suffice to get the prior year's YTD total?
SELECT
t1curr.cod, t1curr.[year], t1curr.[month], t1curr.value, t1prev.value
FROM dbo.Table_1 t1curr
LEFT OUTER JOIN dbo.Table_1 t1prev ON
t1prev.cod = t1curr.cod AND
t1prev.[year] = t1curr.[year] - 1 AND
t1prev.[month] = t1curr.[month]

Assuming "cod" - whatever it is - doesn't change from year to year. If it's a stock ID then the assumption is optimistic.

^{“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw}

For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden