Replacing multiple commas with single comma in MS SQL - sql

Question

How do I replace consecutive commas in a column with single comma in MS SQL?
For example, I have data like
a,,,,b,,,c,,,,,,
d,e,,,f,,,,,,g,,
I want this to be processed to following format:
a,b,c,
d,e,f,g,
The suggested duplicate, Use SQL to Replace Multiple Commas in a String with a Single Comma, is for Oracle. This is a question about SQL Server.

Answer 1

You could use simple REPLACE:
SELECT c, REPLACE(REPLACE(REPLACE(c, ',', '~,'), ',~', ''), '~,', ',')
FROM tab;
DBFiddle Demo
Output:
┌──────────────────┬──────────┐
│ c │ result │
├──────────────────┼──────────┤
│ a,,,,b,,,c,,,,,, │ a,b,c, │
│ d,e,,,f,,,,,,g,, │ d,e,f,g, │
└──────────────────┴──────────┘
Please note that this approach does not depend on SQL dialect and should work with MySQL/Oracle/PostgreSQL/...

Answer 2

It's quite easy to do it with CTE:
declare #s varchar(20) = 'a,,,,b,,,c,,,,,, d,e,,,f,,,,,,g,,'
;with cte as (
select replace(#s, ',,', ',') [s], 1 [rn]
union all
select replace(s, ',,', ',') [s], [rn] + 1
from cte
where LEN(s) - LEN(replace(s, ',,', '')) > 0
)
select top 1 #s = s from cte
order by rn desc
select #s

Answer 3

Although there are very good answers (personally I'd tend to lad2025) I'd like to post another approach (especially as extension to the answer by DruvJoshi)
DECLARE #tbl TABLE(s VARCHAR(100))
INSERT INTO #tbl VALUES('d,e,,,f,,,,,,g,,')
,('a,,,,b,,,c,,,,,,');
SELECT CAST('<x>'+REPLACE(s,',','</x><x>')+'</x>' AS XML)
.query('for $x in /x[text()]
return
<x>
{
concat($x, ",")
}
</x>
')
.value('.','nvarchar(max)') AS result
FROM #tbl;
Short explanation:
The solution uses the well-known XML trick to split a string. The rest is XQuery. The predicate /x[text()] will reduce the nodes to the ones with content. They will be re-created with a comma appended. The .value() with an XPath of . will return one single string of all content within the XML.

Answer 4

please use
SELECT
REGEXP_REPLACE(
REGEXP_REPLACE('Hi,,How are you? Fine, thanks ,, , ,,,, , James,Arden.', ', | ,', ','), --Replace ', ' and ' ,' with ','
',{1,}', ', ') single_comma_text --Replace one or more comma with comma followed by space
FROM DUAL;

Answer 5

Try this Script which eliminates space,multiple commas and give single comma separated as result
DECLARE #tbl AS TABLE (data nvarchar(max))
INSERT INTO #tbl
SELECT 'a,,,,b,,,c,,,,,, ,,,, ,,, ,, ,,,,,d,,,,,,,, ,, d,e,,,f,,,,,,g,,'
;WITH CTE
AS
(
SELECT data
,CAST(LEFT(data,1) AS VARCHAR(10)) AS Letter
,RIGHT(Data,LEN(Data)-1) AS Remainder
FROM #tbl
WHERE LEN(data)>1
UNION ALL
SELECT data
,CAST(LEFT(Remainder,1) AS VARCHAR(10)) AS Letter
,RIGHT(Remainder,LEN(Remainder)-1) AS Remainder
FROM CTE
WHERE LEN(Remainder)>0
)
SELECT STUFF((SELECT ', '+ Letter
FROM
(
SELECT Letter
FROM CTE
WHERE Letter <>',' AND Letter <>''
)dt FOR XML PATH ('')),1,1,'') AS RequiredOutPut
Result
RequiredOutPut
------------------
a, b, c, d, d, e, f, g
Demo : http://rextester.com/VEZS31565

Answer 6

If you can have unknown number of commas I'd recommend splitter using XML path like below.
Assuming you have a table T with column c
also see working demo
Explanation is inline as comments
/* first we split out each letter from each column using XML Path after replacing commas with empty nodes */
; with cte as (
select
id,s
from
(
select
id,
xmldata=cast('<x>'+replace(c,',','</x><x>')+'</x>' as xml) -- conversion to XML from varchar
from t
)A
cross apply
(
select
s = data.D.value('.','varchar(100)')
FROM
A.xmldata.nodes('x') AS data(D)
)c
where s <>''-- filter out empty nodes i.e. commas
)
/* Now we join back results from CTE by adding single comma between letters*/
select distinct id, stuff
((select ','+ s
from cte c1
where c1.id =c2.id
for xml path ('')),1,1,'')
from cte c2

Answer 7

This is what i did.
select replace(replace(replace('a,,,b,,,c,d,e,,,,f',',','<>'),'><',''),'<>',',')

Answer 8

Here is the simple one to suffice all the below cases:
Removing multiple commas in starting of the string
Removing multiple commas at the end of the string
Removing multiple commas to single comma in the middle of the string
select REGEXP_REPLACE(REGEXP_REPLACE(',,LE,,EN,,A,,,','^,*|,*$',''),',{1,}', ', ');
Output :
LE, EN, A