TSQL Pseudo Random text generator

Question

I am doing some performance testing on a SQL sproc and just want to bang out a quick data generator for testing.

I am after a simple way to generate a pseudo random (true random not needed in this case) varchar field.

Ideas I have so far is having a character definition of valid characters that can be used and then build the string from this definition and use a pseudo random length for length variation with a max/min length defined.

Edit:

My test data generator:

DECLARE @MyDataTable TABLE
(
  RecID int IDENTITY(1,1) PRIMARY KEY,
  SomeText varchar(255)
)

DECLARE @RecId int, @SomeText varchar(255),
        @maxlength int, @minlength int, 
        @RecordCount int, @Counter int
SET @maxlength = 254
SET @minlength = 50
SET @RecordCount = 500000
SET @Counter = 1

WHILE (@Counter < @RecordCount)
BEGIN
 INSERT INTO @MyDataTable
 (
  SomeText
 )
 SELECT  TOP 1
 ( 
   select top (abs(checksum(newid())) % (@maxlength-@minlength) + @minlength) char(abs(checksum(newid())) % 26 + ascii('A'))  
   from sys.all_objects a1
   where sign(a1.object_id) = sign(t.object_id) /* Meaningless thing to force correlation */
   for xml path('')
 ) as NewRandomString 
 FROM sys.all_objects t;
 SET @Counter = @Counter + 1
END

Answer 1

I wrote a blog post on this recently.

http://msmvps.com/blogs/robfarley/archive/2009/12/07/randomising-data.aspx

select top (@stringlength) char(abs(checksum(newid())) % 26 + ascii('A')) 
from sys.all_objects 
for xml path('')
;

Edit: Sorry - didn't include the random length thing...

SELECT 
(
  select top (abs(checksum(newid())) % (@maxlength-@minlength) + @minlength) char(abs(checksum(newid())) % 26 + ascii('A')) 
  from sys.all_objects 
  for xml path('')
) as NewRandomString
FROM yourTable; /* Maybe something like dbo.nums? */

Edit: Sorry - needs to be correlated...

SELECT  
( 
  select top (abs(checksum(newid())) % (@maxlength-@minlength) + @minlength) char(abs(checksum(newid())) % 26 + ascii('A'))  
  from sys.all_objects a1
  where sign(a1.object_id) = sign(t.object_id) /* Meaningless thing to force correlation */
  for xml path('')
) as NewRandomString 
,*
FROM sys.all_objects t;

Answer 2

This will generate a random string of variable length.

DECLARE     @text nvarchar(255),
            @length int,
            @i int;
SET @i = 0
SET @text = ''
SET @length = RAND() * 50 + 215
WHILE (@i < @length)
BEGIN
    SET @text = @text + CHAR(RAND() * 26 + 65)
    SET @i = @i + 1
END

Answer 3

For SQL Server 2008

SELECT
    --fixed length
    CAST(CRYPT_GEN_RANDOM(50) AS varchar(100)),
    --variable length
    CAST(CRYPT_GEN_RANDOM(ABS(CHECKSUM(NEWID()))%50) AS varchar(100))

Samples:

r¡Ñ”ã8Ò¯wß×1W=ýÎÜTÜN:Læ*é=Öô/qAtmտ׌1):¢ìèð’¾N
mÁ­BòºÇòWãmßyWßðÛ2ﬔœ¹t ¦2›ÏÀë?î7Ä›››ºªb

My evil twin wants to use this as a password generator...