mysql两个日期相差的天数

CREATE TABLE events (
    id INT AUTO_INCREMENT PRIMARY KEY,
    event_name VARCHAR(255),
    event_date DATE
);

INSERT INTO events (event_name, event_date) VALUES
('Event A', '2023-01-01'),
('Event B', '2023-01-05'),
('Event C', '2023-01-10');

SELECT DATEDIFF(event_date, (SELECT event_date FROM events WHERE event_name = 'Event A')) AS days_diff
FROM events
WHERE event_name = 'Event C';

SELECT DATEDIFF(CONVERT_TZ(event_date, '+00:00', '+08:00'), (SELECT CONVERT_TZ(event_date, '+00:00', '+08:00') FROM events WHERE event_name = 'Event A')) AS days_diff
FROM events
WHERE event_name = 'Event C';

SELECT DATEDIFF(COALESCE(event_date, '1970-01-01'), COALESCE((SELECT event_date FROM events WHERE event_name = 'Event A'), '1970-01-01')) AS days_diff
FROM events
WHERE event_name = 'Event C';