Simple function to recursively replace a pattern in a string.

MSSQL_RepetitiveReplace_fn.sql

CREATE FUNCTION dbo.RepetitiveReplace_fn
(
    @P_String VARCHAR(MAX),
    @P_Pattern VARCHAR(MAX),
    @P_ReplaceString VARCHAR(MAX),
    @P_ReplaceLength INT = 1
)
RETURNS VARCHAR(MAX)
BEGIN
    DECLARE @Index INT;

    -- Get starting point of pattern
    set @Index = patindex(@P_Pattern, @P_String);

    while @Index > 0
    begin
        --replace matching charactger at index
        set @P_String = stuff(@P_String, patindex(@P_Pattern, @P_String), @P_ReplaceLength, @P_ReplaceString);
        set @Index = patindex(@P_Pattern, @P_String);
    end;
    
    return @P_String;
END;