Question

I am wondering if there is a short way (without programming the whole thing) of determining the largest number in a binary value in T-SQL.

In a column I store what days are selected (1 = sunday, 2 = monday, .. 7 = saturday) bitwise.

My translation table:

-- day of week
-- 1 == 1       -> POWER(2,0) -> sunday
-- 2 == 2       -> POWER(2,1) -> monday
-- 3 == 4       -> POWER(2,2)
-- 4 == 8       -> POWER(2,3)
-- 5 == 16      -> POWER(2,4)
-- 6 == 32      -> POWER(2,5)
-- 7 == 64      -> POWER(2,6) -> saturday

So if I select FOR EXAMPLE sunday and saturday my binary value is 65.

How can I select with T-SQL that 65 will be 7??

---

Edit

Lets say I have two record with a two columns:

 ID   | SelectedDays 
------|--------------
 1    | 65
 2    | 3

So, ID 1 will return 7, because that will be the saturday that is selected selected and ID 2 will return monday.

Answer 1

 SELECT FLOOR(LOG(bit_week)/LOG(2))+1

This returns 1 to 7 depending of the date.
logaritm is the inverse of power to obtanin logaritm in base 2, the trick is ‘divide by the base’. FLOOR, in its turn, provides the most significative bit.