In SQL, how can I split the values in a bitmask to

问题:

I have a bitmask value stored as an int in sql. I'd like to turn that value into a comma separated list of the values contained in the bitmask value.

So, for example, the results might look like so:

id  name      bitMaskValue   values
----------------------------------------
1   Bob       5              1,4
2   Mary      13             1,4,8
3   Stan      11             1,2,8

Is there a way to accomplish this in a sql statement?

This is SQL Server 2008.

回答1:

declare @I integer = 2117

Declare @v varChar(32) = ''
Declare @Bit tinyInt = 0
while @I > 0 Begin
Set @v += case @I %2 WHen 1 Then str(@bit,2,1) + ',' else '' End 
Set @Bit += 1
Set @i /= 2
End
Select case  When len(@v) > 0 Then left(@v, len(@v) -1) else '' End

回答2:

This should work:

SELECT id, name, bitMaskValue,
    SUBSTRING(
            CASE WHEN bitMaskValue & 1 = 1 THEN ',1' ELSE '' END
          + CASE WHEN bitMaskValue & 2 = 2 THEN ',2' ELSE '' END
          + CASE WHEN bitMaskValue & 4 = 4 THEN ',4' ELSE '' END
          + CASE WHEN bitMaskValue & 8 = 8 THEN ',8' ELSE '' END
        , 2, 64) As [values]
FROM yourTable

回答3:

CTE + XPATH way:

set nocount on

declare @t as table(id int, name varchar(100), bitMaskValue int)

insert into @t(id, name, bitMaskValue) values(1,'Bob',5)
insert into @t(id, name, bitMaskValue) values(2,'Mary',13)
insert into @t(id, name, bitMaskValue) values(3,'Stan',11)

;with cte(num) as 
(
select 1 
union all
select num*2
from cte
)
select 
    id, 
    name,
    bitMaskValue,
    stuff((
        select cast((
        select isBitSet
        from
        (
            select top 31 num, 
                         case 
                            when bitMaskValue & num = num then ',' + cast(num as varchar(10)) 
                            else null 
                         end isBitSet
            from cte
        ) tmp
        where isBitSet is not null
        for xml path('')) as xml).value('.', 'VARCHAR(max)')
    ), 1, 1, '') bitSet
from @t