For loop in SQL to find 1's position in a sequence of 0's and 1's - sql

Question

Below is the for loop in c# which returns 1's position in a sequence of 0's and 1's here is my code
public string OnesPosition(string statusBits)
{
string onePos = "";
for (int i = 0; i < statusBits.Length; i++)
{
if (statusBits[i] == '1')
{
onePos = onePos + Convert.ToSingle(i + 1) + ",";
}
}
onePos = string.IsNullOrEmpty(onePos ) ? "0," : onePos ;
return onePos;
}
var result = OnesPosition("00000000000101");
This will return: result = 12,14
How I can do this in sql query or using SQL function?
Using SQL Server Management Studio v17.9

Answer 1

Just another option
Example
Declare #S varchar(50) = '00000000000101'
Select Stuff((Select concat(',',N )
From (
Select Top (len(#S)) N=Row_Number() Over (Order By (Select NULL))
From master..spt_values
) s
Where substring(#S,N,1)='1'
Order By N
For XML Path ('')),1,1,'')
Returns
12,14

Answer 2

Loops don't play well in SQL Server, but here is a method.
declare #ones varchar(16) = '00000000100101'
declare #pos int = 1
declare #result varchar(256) = ''
while #pos <= len(#ones)
begin
set #result = #result + case when substring(#ones,#pos,1) = 1 then ',' + cast(#pos as varchar) else '' end
set #pos = #pos + 1
end
select right(#result,len(#result) - 1)

Answer 3

Solution:
Another possible approach is using recursive CTE (which returns each digit and digit positon) and group concatenation.
Using STRING_AGG() (from SQL Server 2017):
DECLARE #ones varchar(16)
SET #ones = '1000000001001011';
WITH Digits AS (
SELECT 1 AS DigitPosition, SUBSTRING(#ones, 1, 1) AS Digit
UNION ALL
SELECT DigitPosition + 1, SUBSTRING(#ones, DigitPosition + 1, 1)
FROM Digits
WHERE DigitPosition < LEN(#ones)
)
SELECT STRING_AGG(DigitPosition, ',')
FROM Digits
WHERE Digit = '1'
Using FOR XML:
DECLARE #ones varchar(16)
SET #ones = '1000000001001011';
WITH Digits AS (
SELECT 1 AS DigitPosition, SUBSTRING(#ones, 1, 1) AS Digit
UNION ALL
SELECT DigitPosition + 1, SUBSTRING(#ones, DigitPosition + 1, 1)
FROM Digits
WHERE DigitPosition < LEN(#ones)
)
SELECT CONVERT(varchar(max), DigitPosition) + ','
FROM Digits
WHERE Digit = '1'
FOR XML PATH('')
Output:
1,10,13,15,16

Answer 4

One more method using a tally table and just straight tsql:
WITH Tally(i) AS (
SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS i
FROM (VALUES (0), (0), (0), (0), (0), (0), (0)) a(n)
CROSS JOIN (VALUES (0), (0), (0), (0), (0), (0)) b(n)
)
SELECT bitloc
FROM
(
SELECT SUBSTRING(x.d, i, 1) as bitset, i bitloc
FROM (VALUES ('00000000000101')) x(d)
CROSS JOIN Tally
) sub
WHERE bitset = 1

Answer 5

Here is function based on #scsimon response and it worked.
CREATE FUNCTION [dbo].[ConvertTo1Positions]
(
#ones AS varchar(16),
#pos AS INT = 1,
#result varchar(256)
) RETURNS VARCHAR(MAX) AS BEGIN
while #pos <= len(#ones)
begin
set #result = #result + iif(substring(#ones,#pos,1) = 1,cast(#pos as char),'')
set #pos = #pos + 1
end
RETURN #result;
END

Answer 6

I don't think it's a good idea to use loop, but since you want it
DECLARE #Str VARCHAR(45) = '000001000000101',
#OutPut VARCHAR(45) = '',
#I INT = 1;
WHILE #I <= LEN(#Str)
BEGIN
IF (SELECT SUBSTRING(#Str, #I, 1)) = '1'
SET #OutPut = #OutPut + (SELECT CAST(#I AS VARCHAR(10))) + ',';
--Convert.ToSingle(i + 1) why +1?
SET #I = #I + 1;
END
SELECT #OutPut;

Answer 7

or this...
DECLARE #string VARCHAR(100) = '00000000000101';
WITH
cte_n1 (n) AS (SELECT 1 FROM (VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) n (n)),
cte_n2 (n) AS (SELECT 1 FROM cte_n1 a CROSS JOIN cte_n1 b),
cte_Tally (n) AS (
SELECT TOP (LEN(#string))
ROW_NUMBER() OVER (ORDER BY (SELECT NULL))
FROM
cte_n2 a CROSS JOIN cte_n2 b
)
SELECT
STRING_AGG(t.n, ',')
FROM
cte_Tally t
WHERE
SUBSTRING(#string, t.n, 1) = '1';