mysql 自定义函数循环

DELIMITER //

CREATE FUNCTION AddNumbers(a INT, b INT)
RETURNS INT
DETERMINISTIC
BEGIN
    RETURN a + b;
END //

DELIMITER ;

SELECT AddNumbers(3, 5); -- 返回 8

DELIMITER //

CREATE FUNCTION CalculateSum(table_name VARCHAR(255), column_name VARCHAR(255))
RETURNS BIGINT
DETERMINISTIC
BEGIN
    DECLARE total_sum BIGINT;
    SET total_sum = (SELECT SUM(column_name) FROM table_name);
    RETURN total_sum;
END //

DELIMITER ;

DELIMITER //

CREATE FUNCTION CalculateSumOptimized(table_name VARCHAR(255), column_name VARCHAR(255), batch_size INT)
RETURNS BIGINT
DETERMINISTIC
BEGIN
    DECLARE total_sum BIGINT;
    DECLARE offset INT DEFAULT 0;
    DECLARE current_sum BIGINT;

    WHILE TRUE DO
        SET current_sum = (SELECT SUM(column_name) FROM table_name LIMIT batch_size OFFSET offset);
        IF current_sum IS NULL THEN
            LEAVE WHILE;
        END IF;
        SET total_sum = total_sum + current_sum;
        SET offset = offset + batch_size;
    END WHILE;

    RETURN total_sum;
END //

DELIMITER ;