Question

Using: SQL Server 2008 R2

My goal is to take a given integer (n) and select every permutation of integers with n bits in 2 columns, as below.

Given: n=4

Output:

ColA  ColB
0     0
0     0
0     0
0     0
1     0
1     0
1     0
1     1
2     0
2     0
2     1
2     0
3     0
3     0
3     1
3     1
...
14    1
14    1
14    1
14    0
15    1
15    1
15    1
15    1

The output does not, repeat does NOT, need to be ordered, which may or may not make this easier. I do, however, need to be able to set n to any integer… but for the sake of runtime, let’s say it’ll be under 10.

Thanks in advance.

Answer 1

You might want to try this:

declare @bits int
set @bits = 4

;with AllTheNumbers as (
    select cast (POWER(2, @Bits) as int) - 1 Number
    union all
    select Number - 1
    from AllTheNumbers
    where Number > 0
),
Bits as (
    select @Bits - 1 Bit
    union all
    select  Bit - 1
    from Bits
    where Bit > 0
)
select *, case when (Number & cast (POWER(2, Bit) as int)) != 0 then 1 else 0 end
from AllTheNumbers cross join Bits
order by Number, Bit desc

AllTheNumbers produces the numbers from 0 to 2^n-1, Bits produces bit numbers from 0 to @Bits – 1 and main part connects them and calculates bit value per position.