MySQL 8.0

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CREATE Function factorial(m INT)
RETURNS BIGINT unsigned DETERMINISTIC
BEGIN
DECLARE factorial BIGINT UNSIGNED DEFAULT 1;
DECLARE counter INT;
SET counter = m;  --  m is my variable
factorial_loop: REPEAT
SET factorial = factorial * counter;
SET counter = counter - 1;
UNTIL counter <= 1
END REPEAT;
RETURN factorial;
END
SELECT factorial(4)/(factorial(4) * factorial(0))


factorial(4)/(factorial(4) * factorial(0))


null


SELECT factorial(4)/(factorial(3) * factorial(1))


factorial(4)/(factorial(3) * factorial(1))


4.0000


SELECT factorial(4)/(factorial(2) * factorial(2))


factorial(4)/(factorial(2) * factorial(2))


6.0000


SELECT factorial(4)/(factorial(1) * factorial(3))


factorial(4)/(factorial(1) * factorial(3))


4.0000


CREATE Function factor(x INT)
RETURNS BIGINT unsigned DETERMINISTIC
BEGIN
DECLARE tempo BIGINT UNSIGNED  DEFAULT 0;
DECLARE counter2 INT;
SET counter2 = x;  --  X is the number of elements, in the example 7
combisum_loop: REPEAT
SET @a := counter2;
SET tempo = tempo + factorial(x)/(factorial(counter2)*factorial(x-counter2));  --  the mathematical formula for k-combinations

SET counter2 = counter2 - 1 ;
UNTIL counter2 <= Y  --  Y is the thresold, in the example 4
END REPEAT;
RETURN tempo;
END
SELECT factor(4)
SELECT @a


@a


4