Question

What’s the best way to do this?

I need to generate a 5 digit length string where all the characters are numeric. However, I need to be able to do this ‘x’ amount of times (user variable) and store this random strings in a database. Furthermore, I can’t generate the same string twice. Old strings will be removed after 6 months.

Pseudo-code

DECLARE @intIterator INT,
 @intMax

SET @intIterator = 1
SET @intMax = 5 (number of strings to generate)

WHILE @intIterator <= @intMax
 BEGIN

  -- GENERATE RANDOM STRING OF 5 NUMERIC DIGITS 
   ???

  -- INSERT INTO DB IF DOESN'T ALREADY EXIST 
  INSERT INTO TSTRINGS
  SELECT @RANDOMSTRING

  IF @@ERROR = 0
    SET @intIterator = @intIterator + 1

 END

I know this probably isn’t the best way to do it, so advice is appreciated. But really looking for ideas on how to generate the numeric 5 length strings.

Answer 1

All in one. This should find the @intMax remaining values if you have (100000 – @intMax) rows already with just @intMax permutations left

INSERT TOP (@intMax) MyTable (RndColumn)
SELECT
    RndValue
FROM
    (
    SELECT DISTINCT TOP 100000 -- covers potential range from 00000 to 99999
        RIGHT('00000' + CAST(ABS(CHECKSUM(NEWID())) AS varchar(10)), 5) AS RndValue
    FROM
        sys.columns c1, sys.columns c2
    ) foo
WHERE
    NOT EXISTS (SELECT *
        FROM
            MyTable T
        WHERE
            T.RndColumn = foo.RndValue