Parsing / Indexing a Binary String in SQL Server - sql

Question

I have searched extensively for a relevant answer, but none quite satisfy what I need to be doing.
For our purposes I have a column with a 50 character binary string. In our database, it is actually hundreds of characters long.
There is one string for each unique item ID in our database. The location of each '1' flags a specific criteria being true, and a '0' false, so the indexed location of the ones and zeros are very important. Mostly, I care about where the 1's are.
I am not updating any databases, so I first decided to try and make a loop to look through each string and create a list of the 1's locations.
declare #binarystring varchar(50) = '10000010000110000001000000000000000000000000000001'
declare #position int = 0
declare #list varchar(200) = ''
while (#position <= len(#binarystring))
begin
set #position = charindex('1', #binarystring, #position)
set #list = #list + ', ' + convert(varchar(10),#position)
set #position = charindex('1', #binarystring, #position)+1
end
select right(#list, len(#list)-2)
This creates the following list:
1, 7, 12, 13, 20, 50
However, the loop will bomb if there is not a '1' at the end of the string, as I am searching through the string via occurrences of 1's rather than one character at a time. I am not sure how satisfy the break criteria when the loop would normally reach the end of the string, without there being a 1.
Is there a simple solution to my loop bombing, and should I even be looping in the first place?
I have tried other methods of parsing, union joining, indexing, etc, but given this very specific set of circumstances I couldn't find any combination that did quite what I needed. The above code is the best I've got so far.
I don't specifically need a comma delimited list as an output, but I need to know the location of all 1's within the string. The amount of 1's vary, but the string size is always the same.
This is my first time posting to stackoverflow, but I have used answers many times. I seek to give a clear question with relevant information. If there is anything I can do to help, I will try to fulfill any requests.

Answer 1

How about changing the while condition to this?
while (charindex('1', #binarystring, #position) > 0)

Answer 2

while (#position <= len(#binarystring))
begin
set #position = charindex('1', #binarystring, #position)
if #position != 0
begin
set #list = #list + ', ' + convert(varchar(10),#position)
set #position = charindex('1', #binarystring, #position)+1
end
else
begin
break
end;
end

Answer 3

It's often useful to have a source of large ranges of sequential integers handy. I have a table, dbo.range that has a single column, id containing all the sequential integers from -500,000 to +500,000. That column is a clustered primary key so lookups against are fast. With such a table, solving your problem is easy.
Assuming your table has a schema something like
create table dbo.some_table_with_flags
(
id int not null primary key ,
flags varchar(1000) not null ,
)
The following query should do you:
select row_id = t.id ,
flag_position = r.id
from dbo.some_table t
join dbo.range r on r.id between 1 and len(t.flags)
and substring(t.flags,r.id,1) = '1'
For each 1 value in the flags column, you'll get a row containing the ID from your source table's ID column, plus the position in which the 1 was found in flags.
There are a number of techniques for generating such sequences. This link shows several:
http://sqlperformance.com/2013/01/t-sql-queries/generate-a-set-1
For instance, you could use common table expressions (CTEs) to generate your sequences, like this:
WITH
s1(n) AS -- 10 (10^1)
( SELECT 1
UNION ALL SELECT 1
UNION ALL SELECT 1
UNION ALL SELECT 1
UNION ALL SELECT 1
UNION ALL SELECT 1
UNION ALL SELECT 1
UNION ALL SELECT 1
UNION ALL SELECT 1
UNION ALL SELECT 1
) ,
s2(n) as ( select 1 from s1 a cross join s1 b ) , -- 10^2 100
s3(n) as ( select 1 FROM s1 a cross join s2 b ) , -- 10^3 1,000
s4(n) as ( select 1 from s1 a cross join s3 b ) , -- 10^4 10,000
s5(n) as ( select 1 from s1 a cross join s4 b ) , -- 10^5 100,000
s6(n) as ( select 1 from s1 a cross join s5 b ) , -- 10^6 1,000,000
seq(n) as ( select row_number() over ( order by n ) from s6 )
select *
from dbo.some_table t
join seq s on s.n between 1 and len(t.flags)
and substring(t.flags,s.n,1) = '1'