In this section, I will make an example of a procedure that recursively calculates factorial in SQL Server.

First, let’s talk about what factorial is.

The product of numbers starting from 1 up to a certain counting number is called the factorial of that number.

For example, the factorial of 5 (denoted by 5!): 120 = 5 * 4 * 3 * 2 * 1.

What is recursive?

If a structure has the ability to refer to itself, such structures are called recursive structures.

Now let’s move on to the code example.

CREATE PROCEDURE CalculateFactorial
(
    @Number INTEGER,
    @Result INTEGER OUTPUT
)
AS
DECLARE @Input INTEGER;
DECLARE @Output INTEGER;
IF @Number != 1
BEGIN
    SELECT @Input = @Number - 1;
    EXEC FaktoriyelHesapla @Input, @Output OUTPUT;
    SELECT @Result = @Number * @Output;
END;
ELSE
BEGIN
    SELECT @Result = 1;
END;
RETURN; 

--Çalıştırılması 

DECLARE @Result INTEGER;
EXEC CalculateFactorial @Number = 5,              -- integer 
                       @Result = @Result OUTPUT; -- integer 
PRINT @Result;

When you create and run the above procedure, you will see a result similar to the one below.

As can be seen, we have calculated the factorial recursively.

Good luck to everyone in business and life.

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