SQL Functions - factorial

Question

I am a beginner in SQL Functions. What is the best way to create a function for factorial in SQL Server- Say 10!

Answer 1

-- Iterative method. -- Why Iterative? It is simpler and faster. -- For @N from 0 to 20 this gives an exact result. -- 21 will give an overflow.

DECLARE @N Bigint = 20
DECLARE @F Bigint = 1
WHILE @N > 0 BEGIN
  SET @F = @f*@n
  SET @N = @N-1
END
SELECT @F AS FACTORIAL

-- Change the datatype to float and you can get the factorial up to 170. -- 171 will result in an overflow. -- Remark the result will only be accurate over a limited number of positions.

DECLARE @N FLOAT = 170
DECLARE @F FLOAT = 1
WHILE @N > 0 BEGIN
  SET @F = @f*@n
  SET @N = @N-1
END
SELECT @F AS FACTORIAL

-- Ben