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

Another way:

create function Fact(@num int)
returns bigint
as
begin
declare @i int = 1

 while @num>1
 begin
  set @i = @num *  @i
  set @num=@num-1
  end

return @i
end

select dbo.Fact(5)