Question

I’m a bit lost with the following problem that I need to solve with an SQL query, no plsql. The idea is to build a cumulative column to calculate all previous months. The input table looks like

 Month
 1
 2
 3
 ..
 24

I need build the following table :

Month Cum_Month
1     1
2     1
2     2
3     1
3     2
3     3
..
24    1
...
24    23

All this in SQL Server 2008, thanks in advance

Answer 1

You can do it like this:

DECLARE @tbl TABLE ([Month] INT)
INSERT @tbl VALUES
(1),(2),(3),(4),(5),(6),(7),(8),(9),(10),
(11),(12),(13),(14),(15),(16),(17),(18),(19),(20),(21),(22),(23),(24)


SELECT  Month
        ,   ROW_NUMBER() OVER (PARTITION BY Month ORDER BY Month) num
FROM    @tbl a
JOIN    
(
    SELECT  *
    FROM    master..spt_values 
    WHERE   type = 'P'
)
b ON b.number < a.Month

master..spt_values is used to generate numbers, after numbers are generated result of the subquery is joined on the @tbl to get the number of rows that corresponds to the month. After that ROW_NUMBER is used to create appropriate ordinal numbers for each month.