DECLARE @SpecialSymbols TABLE (Symbol CHAR(1) NOT NULL PRIMARY KEY)
INSERT @SpecialSymbols VALUES ('#'), ('$'), ('['), (']'), ('%'), ('^'),( '*'),('('),('_'), ('"')

DECLARE @TestData TABLE (StringToTest VARCHAR(100))
INSERT @TestData VALUES ('ABS.DRG.drg.name[ABS.PAT.number%4]'), ('.PAT.number%4]'), 
('test 1 [Using Square Brackets]'), ('[Test2@EmailAddress.com]'), ('No Special Symbols')
    
  SELECT  StringToTest, MIN(Position) pos
    FROM    @TestData
            OUTER APPLY
            ( SELECT  CHARINDEX(Symbol, StringToTest) [Position], Symbol
                FROM    @SpecialSymbols
            ) Symbols
    WHERE   Position > 0
	GROUP BY StringToTest

-- This is for getting all special character's position
DECLARE @SpecialSymbols TABLE (Symbol CHAR(1) NOT NULL PRIMARY KEY)
INSERT @SpecialSymbols VALUES ('#'), ('$'), ('['), (']'), ('%'), ('^'),( '*'),('('),('_'), ('"')

DECLARE @TestData TABLE (StringToTest VARCHAR(100))
INSERT @TestData VALUES ('ABS.DRG.drg.name[ABS.PAT.number%4]'), ('.PAT.number%4]'), 
('test 1 [Using Square Brackets]'), ('[Test2@EmailAddress.com]'), ('No Special Symbols')

;WITH CTE AS
(   SELECT  *, STUFF(StringToTest, Position, 1, ' ') [ReworkedString]
    FROM    @TestData
            OUTER APPLY
            (   SELECT  CHARINDEX(Symbol, StringToTest) [Position], Symbol
                FROM    @SpecialSymbols
            ) Symbols
    WHERE   Position > 0
    UNION ALL
    SELECT  StringToTest, Symbols.Position, Symbols.Symbol, STUFF(ReworkedString, Symbols.Position, 1, ' ') [ReworkedString]
    FROM    CTE
            OUTER APPLY
            (   SELECT  CHARINDEX(Symbol, ReworkedString) [Position], Symbol
                FROM    @SpecialSymbols
                WHERE   Symbol = CTE.Symbol
            ) Symbols
    WHERE   Symbols.Position > 0
)
SELECT  a.StringToTest, COALESCE(Location, '') [SpecialSymbolLocations]
FROM    @TestData a
        LEFT JOIN
        (   SELECT  DISTINCT
                    StringToTest,
                    -- THIS MERELY CONCATENATES ROWS INTO COLUMNS TO GET COMMA SEPARATED LIST
                    STUFF(( SELECT  ', ' + CONVERT(VARCHAR, Position)
                            FROM    CTE b
                            WHERE   a.StringToTest = b.StringToTest
                            ORDER BY Position
                            FOR XML PATH('')
                    ), 1, 2, '') [Location] 
            FROM    CTE a
        ) b
            ON a.StringToTest = b.StringToTest