extract all decimal value from a string in sql server - sql

Question

I want to extract all decimal values from a string:
'1.1aa' = 1.1,
'-1.1al3' = -1.13,
' -' = 0
'21d.2 d .3-d' = 21.23
What will be the query to extract this output?
DECLARE #Col VARCHAR(100)='-c 43.f4gh57t';
While (PATINDEX('%[^0-9.-]%', #Col) > 0)
begin
SET #Col = STUFF(#Col, PATINDEX('%[^-0-9.]%', #Col), 1, '');
end
SELECT CAST(#Col AS DECIMAL(18, 2));
I have written this query but it is not working with these values:
' -',
'21d.2 d .3-d'

Answer 1

DECLARE #Col VARCHAR(100)= '--A12345-..6789-.';
While (PATINDEX('%[^0-9.-]%', #Col) > 0)
begin
SET #Col = STUFF(#Col, PATINDEX('%[^-0-9.]%', #Col), 1, '');
end
--remove all hyphens but keep the first one (if first char with numbers following)
select #Col = case when #Col like '-%[0-9]%' then '-' else '' end + replace(#Col, '-', '')
where #Col like '%-%';
--remove all dots but keep the first one (if followed by numbers)
select #Col = stuff(replace(#Col, '.', '')+' ', charindex('.', #Col), 0, case when #Col like '%.%[0-9]%' then '.' else '' end)
where #Col like '%.%';
select #col as _col;
SELECT CAST(case when #col = '' then '0' else #col end AS DECIMAL(20,10)) as _decimal;

Answer 2

You could do this with Tally, though if you have multiple '.' characters or a '-' in the middle of the string it will fail on conversion:
DECLARE #Value varchar(100) = '-c 43.f4gh57t';
WITH N AS(
SELECT N
FROM (VALUES(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL))N(N)),
Tally AS(
SELECT TOP (LEN(#Value))
ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS I
FROM N N1, N N2),
Chars AS(
SELECT T.I,
SUBSTRING(#Value,T.I,1) AS C
FROM Tally T)
SELECT TRY_CONVERT(decimal(25,10),STRING_AGG(C.C,'') WITHIN GROUP (ORDER BY C.I)) AS Number
FROM Chars C
WHERE C.C LIKE '[0-9.-]';
If you're using an older version of SQL Server, you'll need to use the "old" FOR XML PATH (and STUFF) technique instead of STRING_AGG.
Version 2: This should eliminate the errors I describe above:
DECLARE #Value varchar(100) = '-c 4-3.f4gh.57t';
WITH N AS(
SELECT N
FROM (VALUES(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL))N(N)),
Tally AS(
SELECT TOP (LEN(#Value))
ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS I
FROM N N1, N N2),
Chars AS(
SELECT T.I,
SUBSTRING(#Value,T.I,1) AS C
FROM Tally T),
RNs AS(
SELECT C.C,
ROW_NUMBER() OVER (ORDER BY C.I) AS RN,
ROW_NUMBER() OVER (PARTITION BY C.C ORDER BY C.I) AS cRN
FROM Chars C
WHERE C.C LIKE '[0-9.-]')
SELECT TRY_CONVERT(decimal(25,10),STRING_AGG(V.C,'') WITHIN GROUP (ORDER BY R.RN)) AS Number
FROM RNs R
CROSS APPLY (VALUES(CASE R.C WHEN '-' THEN CASE R.RN WHEN 1 THEN R.C END
WHEN '.' THEN CASE R.cRN WHEN 1 THEN R.C END
ELSE R.C
END))V(C);