DECLARE @VALUE AS VARCHAR(20) = \'ABCD\' --Mention the text which is to be permuted
DECLARE @NoOfChars AS INT = LEN(@VALUE)
DECLARE @Permutations TABLE(VALUE VARCHAR(20)) --Make sure the size of this Value is equal to your input  string length (@Value)


;WITH NumTally AS (--Prepare the Tally Table to separate each character of the Value.
  SELECT 1 Num
  UNION ALL
  SELECT
    Num + 1
  FROM
    NumTally
  WHERE
    Num < @NoOfChars
),Chars AS ( --Separate the Characters
SELECT
  Num,
  SUBSTRING(@VALUE,Num,1) Chr
FROM
  NumTally
)

--Persist the Separated characters.

INSERT INTO @Permutations
SELECT Chr FROM Chars

--Prepare Permutations

DECLARE @i AS INT = 1
WHILE(@i < @NoOfChars)
BEGIN

  --Store the Permutations

  INSERT INTO @Permutations
  SELECT DISTINCT --Add DISTINCT if required else duplicate Permutations will be generated for Repeated  Chars.
    P1.VALUE + P2.VALUE
  FROM
    (SELECT VALUE FROM @Permutations WHERE LEN(VALUE) = @i) P1
  CROSS JOIN
    (SELECT VALUE FROM @Permutations WHERE LEN(VALUE) = 1) P2

  --Increment the Counter.
  SET @i += 1

  --Delete the Incorrect Lengthed Permutations to keep the table size under control.
  DELETE FROM @Permutations WHERE LEN(VALUE) NOT IN (1,@i)

END

--Delete InCorrect Permutations.

SET @i = 1

WHILE(@i <= @NoOfChars)
BEGIN

  --Deleting Permutations which has not used "All the Chars of the given Value".
  DELETE
  FROM
    @Permutations
  WHERE
    VALUE NOT LIKE \'%\' + SUBSTRING(@VALUE,@i,1) +\'%\'


  --Deleting Permutations which have repeated incorrect character.
  DELETE
  FROM
    @Permutations
  WHERE
    LEN(VALUE) - LEN(REPLACE(VALUE,SUBSTRING(@VALUE,@i,1),\'\')) !=
    LEN(@VALUE) - LEN(REPLACE(@VALUE,SUBSTRING(@VALUE,@i,1),\'\'))

  SET @i += 1

END

--Selecting the generated Permutations.
SELECT VALUE FROM @Permutations