avg sale of quarter with previous quarter avg sale

Question

I have a table one in which there are various attribute like region product,year,qtr,month,sale. I have to calculate the avg_qtr sale of each product having same region and

Answer 1

You need to join on some sub-select statements that will get the previous quarter avg. You will also need to do a union of two statements because for quarters 2,3,4 you can simply subtract a quarter on the join statement to the previous qtr avg, but when it is the 1st quarter you need to subtract a year and set the previous qtr = 4. This statement should work for what you have described.

--handles when the current quarter being viewed is 2,3,or 4 because those would still be in the same year when looking at the previous quarter
select  t1.product,
        t1.year,
        t1.month,
        t1.sales ,
        t1.qtr,
        round(avg(t1.sales) over (partition by t1.qtr,t1.year),2) as av,
        t2.prev_av
from one t1
left join ( select
                product,
                year,
                month,
                sales ,
                qtr,
                round(avg(sales) over (partition by qtr,year),2) as prev_av
            from one
            ) t2
on t1.year = t2.year
and (t1.qtr - 1) = t2.qtr
where t1.qtr in (2,3,4)
union
--handles the 1st quarter of the year when you need to grab the 4th quarter of the previous year for the previous avg
select  t3.product,
        t3.year,
        t3.month,
        t3.sales ,
        t3.qtr,
        round(avg(t3.sales) over (partition by t3.qtr,t3.year),2) as av,
        t4.prev_av
from one t3
left join ( select
                product,
                year,
                month,
                sales,
                qtr,
                round(avg(sales) over (partition by qtr,year),2) as prev_av
            from one
            ) t4
on (t3.year - 1) = t4.year
and t4.qtr = 4
where t3.qtr = 1;