date computation from weekno and a column value

Analytics
Enthusiast

date computation from weekno and a column value

Hi,

I have a table with the following structure
a
b
c
wkno
sun_1
mon_2
tue_3
wed_4
thu_5
fri_6
sat_7

I need to select abc for a particular date but don't have column that would specify the date. It just a weekno and split up of days. Based on the column value for sun_1,mon_2,tue_3,wed_4,thu_5,fri_6, sat_7 i need to frmulate the date.

For example if i have a value >0 for any of the days then the weekno+the day(sun_1 for ex) will give a date.

For example weekno 10000 indicates 1 week of 2009
then if Sat_7 has a value >0 the date would be 3-Jan-2009.

How do i write a sql to do this? Also i would have tod o this for a 200 million rows so the performance is also a major consideration. Is there any function that could do this???