Generating the same random string in SQL for a set of rows

If it's just for testing purpose and a matter of interest, I'd do it like that:

1. Put distinct records into temporary table and add a new column, let's name it [Randomized]
2. Generate desired random text and make sure it has same LEN() as actual text (Use LEFT(), RIGHT(), SUBSTRING() or any other function to do that)
3. Query your actual table and join them on your predicate.
4. Update your actual table with randomized columns

Not sure if it fits your needs or not.

Here is one method: Do a checksum() on the string and choose the first characters.

select left(cast(checksum(name) as varchar(255)), 10)

The result will only be strings with digits, but that seems to meet your requirement.

You can use a hashing function to replace the values. You may want to keep a key so that you can reverse the the functions. That being said it sounds like you simply want to obfuscate. You can do this using any number of hash functions in most sql languages.You could consider md5, sha1, or sha2 or some other.

In sql-server hashbytes has MD2, MD4, MD5, SHA, SHA1, or SHA2 I believe.

You can obfuscate your data like this:

select HASHBYTES('MD5', 'Sample String to hash ') from x;
select HASHBYTES('SHA1', 'Sample String to hash ') from x;

These algorithms are designed to reduce collisions. Md5 is much less secure.

I would recommend CRC32 which returns the cyclic redundancy check value of a given string as a 32-bit unsigned value when your data isn't sensitive. It can be used as a hash function but again is not secure. It does give a smaller string so is more efficient when reversebility is not an issue.

select CHECKSUM('string') from x;

I was curious... What about this:

EDIT: You could use this to find a "new value" for each distinct existing value...

CREATE VIEW Get_NewID
AS
SELECT NEWID() AS MyNewID
GO

CREATE FUNCTION dbo.RandomLetters(@Length INT)
RETURNS VARCHAR(MAX)
AS
BEGIN
DECLARE @rslt VARCHAR(MAX);
WITH TwentySixNumbers AS
(
    --a tally table
    SELECT TOP 26 ROW_NUMBER() OVER(ORDER BY object_id) AS nmbr
                 ,(SELECT MyNewID FROM Get_NewID) AS sort
    FROM sys.objects
)
,TwentySixLetters AS
(
    SELECT nmbr,sort,CHAR(nmbr+64) AS letter
    FROM TwentySixNumbers
)
SELECT @rslt=
(
    SELECT TOP (@Length) letter
    FROM TwentySixLetters
    ORDER BY sort
    FOR XML PATH(''),TYPE
).value('.','varchar(max)');
RETURN @rslt;
END
GO

--Here you create 10 different strings of seven letters
--pass as length the length of your text
WITH TenNumbers AS
(
    --a tally table
    SELECT TOP 10 ROW_NUMBER() OVER(ORDER BY object_id) AS nmbr
    FROM sys.objects
)
SELECT dbo.RandomLetters(7)
FROM TenNumbers;