PMT Function (Payment) - SQL Server

PMT.sql

/** 
 * Payment (PMT)
 * (SQL Server)
 * AzsaturnDx (2020) - No copyright at all
 *
 * Calculates the payment for a loan based on constant payments and a constant interest rate.
 *
 * @Rate FLOAT - Required. The interest rate for the loan.
 * @Periods INT - Required. The total number of payments for the loan.
 * @Present FLOAT - Required. The present value, or the total amount that a series of future payments is worth now; also known as the principal.
 * @Future FLOAT - Optional. The future value, or a cash balance you want to attain after the last payment is made. If fv is omitted, it is assumed to be 0 (zero), that is, the future value of a loan is 0.
 * @Type INT - Optional. The number 0 (zero) or 1 and indicates when payments are due. (0 = End of Period , 1 = Start of Period)
 * @return FLOAT Payment
 *
 * @Example
 * 	  SELECT dbo.PMT(.20,12,1,2,0)
 *
 * More financial functions are available @: https://gist.github.com/Azsaturndx/8ce3e47e2d3210a65fc83b09ac32da5f
 */


CREATE FUNCTION [dbo].[PMT]
	(@Rate FLOAT
	,@Periods INT
	,@Present FLOAT
	,@Future FLOAT
	,@Type INT)  
RETURNS FLOAT
    BEGIN   
	    SET @Type = ISNULL(@Type, 0);
		SET @Future = ISNULL(@Future, 0);
		DECLARE @Result AS FLOAT = 0;
		DECLARE @Term AS FLOAT = 0;

		IF @Rate=0
		BEGIN
			SET @Result=(@Present+@Future)/@Periods;
		END --IF @Rate=0
		ELSE
		BEGIN --IF @Rate <> 0
			SET @term = POWER(1+@rate, @periods);
			
			IF @Type=1
			BEGIN
				SET @Result = (@Future*@Rate / (@Term-1) + @Present*@Rate / (1-1/@Term)) / (1+@Rate)
			END
			
			ELSE
			BEGIN
				SET @Result = @Future*@Rate/(@term-1)+@Present*@Rate / (1-1/@Term)
			END

		END --IF @Rate <> 0

        RETURN -@Result  
    END;