Removing repeated duplicated characters

Question

I have a string in my stored proc like \',,,sam,,bob,\' or \',,,\' from the above string I have to delete multiple commas from it, it must look like <

Answer 1

Your solutions are good but

1. it is comma only
2. i hate loop-based TSQL code ;-)

so i wrote based on Marcin solution set-based universal code for replacement of every declared kind of duplicates:

DECLARE @Duplicate NVARCHAR(100)= '#$'
DECLARE @TestString NVARCHAR(MAX)= 'test_test__f##f2$$g'
DECLARE @Replacement NVARCHAR(MAX)= ''
DECLARE @OutputString NVARCHAR(MAX)= @teststring ;
WITH    numbers
          AS ( SELECT   ROW_NUMBER() OVER ( ORDER BY o.object_id, o2.object_id ) Number
               FROM     sys.objects o
                        CROSS JOIN sys.objects o2
             ),
        chars
          AS ( SELECT   SUBSTRING(@Duplicate, 1, 1) CHAR ,
                        CAST(1 AS INT) [LEVEL]
               UNION ALL
               SELECT   SUBSTRING(@Duplicate, numbers.Number, 1) CHAR ,
                        CAST(numbers.Number AS INT) [LEVEL]
               FROM     numbers
                        JOIN chars ON chars.Level + 1 = numbers.Number
               WHERE    LEN(SUBSTRING(@Duplicate, numbers.Number, 1)) > 0
             ),
        Replicated
          AS ( SELECT   REPLICATE(CHAR, numbers.number) Repl ,
                        numbers.Number
               FROM     chars
                        CROSS JOIN numbers
             )
    SELECT  @OutputString = REPLACE(@OutputString, Repl, @Replacement)
    FROM    replicated
    WHERE   number <= LEN(@TestString)

SELECT  @OutputString

You can declare every kind of char in Duplicate string and every replacement string in @Replacement. Additional gain IMHO is that i search for replacement only in range of maximum length of input string