Sunday, May 26, 2013

MSSQL: Generate Random String Using SQL

The following will generate a random fixed-length string using SQL. Simply pass in a string of accepted characters and the length of the random string to be generated.

IF ISNULL(object_id('cspRandomString'),0)<>0 DROP PROC cspRandomString
IF ISNULL(object_id('fnGenRandomInteger'),0)<>0 DROP FUNCTION fnGenRandomInteger
GO
CREATE function fnGenRandomInteger(@MinValue int, @MaxValue int, @Seed float)
returns int
as
begin
-- =============================================
-- Author:        Loh Hon Chun
-- =============================================
 return ((@MaxValue + 1) - @MinValue) * @Seed + @MinValue
end
go
CREATE procedure cspRandomString (
 @Result varchar(255) output,
 @AcceptedChars varchar(255),
 @Length int
)
as
begin
-- =============================================
-- Author:        Loh Hon Chun
-- =============================================
 set nocount on

 declare @ret char(255)
 declare @i int, @pos int
 
 set @Result = ''
 set @i = 0

 if LEN(@AcceptedChars) > 0
 begin
  while @i < @Length
  begin
   set @pos = dbo.fnGenRandomInteger(1, LEN(@AcceptedChars), RAND(CONVERT(VARBINARY, NEWID())))
   set @Result = @Result + CAST(SUBSTRING(@AcceptedChars, @pos, 1) AS VARCHAR(1))
   set @i = @i + 1
  end
 end
end
go

declare @result varchar(255)
declare @acceptedChars varchar(255)
declare @length int

set @acceptedChars = '0123456789'
set @length = 7
exec cspRandomString @Result=@result output, @AcceptedChars=@acceptedChars, @Length=@length
print @result
go

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