Creating Nondeterministic functions in SQL Server using RAND()

Question

After a bit of searching and reading the documentation, it\'s clear that you can write user defined functions in SQL Server that are marked as either deterministic or nondet

Answer 1

Because it has side effects.

Constructs with side effects are not allowed in a function. The side effect that it has is to change some internal state that keeps track of the last rand() value issued.

I think you can get around it by including it in a View definition then selecting from the View.

Answer 2

I found this solution that doesn't create a view:

Basically:

Instead of

SET @R = Rand()

Use

SET @R = ABS(CHECKSUM(PWDENCRYPT(N''))) / 2147483647.0

In my case I wanted a number between 1 and 10:

ROUND(((10 - 1 -1) * ( ABS(CHECKSUM(PWDENCRYPT(N''))) / 2147483647.0) + 1), 0))

ROUND(((@max - @lower -1) * ( ABS(CHECKSUM(PWDENCRYPT(N''))) / 2147483647.0) + @lower), 0))

If you want a full explanation: Using (Or Simulating) Rand() In A T-Sql User-Defined Function

Answer 3

Using a View might work for you.
From Returning Random Numbers from a select statement

CREATE VIEW vRandNumber
AS
SELECT RAND() as RandNumber

The view is necessary because, as you already found out, a UDF cannot use the rand() function because that would make the function non-determistic. You can trick the UDF to accept a random number by using a View.

CREATE FUNCTION RandNumber()
RETURNS float
AS
  BEGIN
  RETURN (SELECT RandNumber FROM vRandNumber)
  END

Finally, you can use this function in any SELECT to now return a random number between 0 and 1 per row:

SELECT dbo.RandNumber(), *
FROM Northwind..Customers