Given a series of email addresses, I need to randomly pair them with the condition that if A is to give a gift to B, then B must give a gift to A. If the number of email addresses is odd, the last three must be paired with each other (A with B, B with C, and C with A). I’m implementing this in MySQL with the following code:

CREATE TABLE IF NOT EXISTS CasoB(
    id INT PRIMARY KEY AUTO_INCREMENT,
    persons VARCHAR(50),
    personsToGive VARCHAR(50) 
);

INSERT INTO CasoB (persons, personsToGive) VALUES 
('a.tomas', NULL),
('g.rubio', NULL),
('a.pulido', NULL),
('m.fabrega.1', NULL),
('d.lazaro', NULL),
('c.albinya', NULL),
('b.gomez', NULL),
('j.espinoza', NULL),
('j.aguilera', NULL),
('j.da.silva.1', NULL),
('a.chamorro', NULL);

DELIMITER //

CREATE OR REPLACE PROCEDURE GenerateRandomOrderB()
BEGIN
    DECLARE lineCount INT;

    -- Drop the temporary table if it exists
    DROP TEMPORARY TABLE IF EXISTS RandomOrderB;

    -- Create the temporary table
    CREATE TEMPORARY TABLE IF NOT EXISTS RandomOrderB (
        id INT PRIMARY KEY,
        persons VARCHAR(50),
        RowNumber INT,
        TotalCount INT
    );

    -- Get the number of lines in CasoB
    SELECT COUNT(*) INTO lineCount FROM CasoB;

    -- Insert data into the temporary table and get the total count
    INSERT INTO RandomOrderB (id, persons, RowNumber, TotalCount)
    SELECT  id, 
            persons,
            ROW_NUMBER() OVER(ORDER BY RAND()) AS RowNumber,
            lineCount AS TotalCount
    FROM    CasoB;

    IF lineCount % 2 = 0 THEN
        -- Even number of records
        -- Pair the persons
        UPDATE CasoB
        SET personsToGive = (
            SELECT r2.persons
            FROM RandomOrderB AS r1
            INNER JOIN RandomOrderB AS r2
            ON r2.RowNumber = r1.RowNumber + (lineCount / 2)
            WHERE r1.id = CasoB.id
        );
    ELSE
        -- Odd number of records
        -- Pair all persons except the last three
        UPDATE CasoB
        SET personsToGive = (
            SELECT r2.persons
            FROM RandomOrderB AS r1
            INNER JOIN RandomOrderB AS r2
            ON r2.RowNumber = r1.RowNumber + (lineCount / 2)
            WHERE r1.id = CasoB.id
        );

        -- Pair the last three persons among themselves
        UPDATE CasoB
        SET personsToGive = persons
        WHERE id IN (
            SELECT id
            FROM (
                SELECT id
                FROM RandomOrderB
                ORDER BY RowNumber DESC
                LIMIT 3
            ) AS lastThree
        );
    END IF;
    
    -- Drop the temporary table when finished
    DROP TEMPORARY TABLE IF EXISTS RandomOrderB;
END //

DELIMITER ;