T-SQL Divide value across rows

Question

I have the following columns and data in table:

PeriodID Days
1        NULL
2        NULL
3        NULL
4        NULL
5        NULL

Then I have days that should divide across the rows as follows:

1. If Days < 5 (for example 2) I will have:

   PeriodID Days
   1        NULL
   2        NULL
   3        NULL
   4        1
   5        1
   

2. If days >= 5 and days%5=0 (for example 5) I will have:

   PeriodID Days
   1        1    
   2        1    
   3        1    
   4        1    
   5        1
   

3. If days > 5 and days%5!=0 (for example 12) I will have:

   PeriodID Days
   1        3    
   2        3    
   3        2    
   4        2    
   5        2
   

I am able doing this with loops, and I hope for better solution using some smart technique or T-SQL function. Thanks in advance.

Answer 1

This should do it for you:

DECLARE @numDays int
SET @numDays = 12

UPDATE someTable
SET Days = CASE WHEN @numDays < 5 
                  THEN CASE WHEN @numDays >= 6 - PeriodId THEN 1 ELSE NULL END
                ELSE FLOOR((@numDays + 5 - PeriodId) / 5)
           END