创建显示时间格式"00:00:00“的SQL函数

CREATE FUNCTION display_time_format(time_val TIME)
RETURNS VARCHAR(8)
BEGIN
    DECLARE hour_val INT;
    DECLARE min_val INT;
    DECLARE sec_val INT;
    DECLARE time_str VARCHAR(8);
    
    SET hour_val = HOUR(time_val);
    SET min_val = MINUTE(time_val);
    SET sec_val = SECOND(time_val);
    
    SET time_str = CONCAT(
        LPAD(hour_val, 2, '0'), ':',
        LPAD(min_val, 2, '0'), ':',
        LPAD(sec_val, 2, '0')
    );
    
    RETURN time_str;
END;

SELECT display_time_format('12:34:56');