Question

UPDATE CattleProds
SET SheepTherapy=(ROUND((RAND()* 10000),0))
WHERE SheepTherapy IS NULL

If I then do a SELECT I see that my random number is identical in every row. Any ideas how to generate unique random numbers?

Answer 1

Instead of rand(), use newid(), which is recalculated for each row in the result. The usual way is to use the modulo of the checksum. Note that checksum(newid()) can produce -2,147,483,648 and cause integer overflow on abs(), so we need to use modulo on the checksum return value before converting it to absolute value.

UPDATE CattleProds
SET    SheepTherapy = abs(checksum(NewId()) % 10000)
WHERE  SheepTherapy IS NULL

This generates a random number between 0 and 9999.