MySQL datetime vs timezone

create-db.sql

# Create and insert data 
CREATE TABLE `datetime_timestamp` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `datetime_value` datetime NOT NULL,
  `timestamp_value` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `inputted_timezone` varchar(255) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

SET @@time_zone = 'SYSTEM';
INSERT INTO datetime_timestamp (datetime_value, timestamp_value, inputted_timezone) 
VALUES ('2020-01-01 10:10:10', '2020-01-01 10:10:10', "SET @@time_zone = 'SYSTEM'");

SET @@time_zone = '+07:00';
INSERT INTO datetime_timestamp (datetime_value, timestamp_value, inputted_timezone) 
VALUES ('2020-01-01 10:10:10', '2020-01-01 10:10:10', "SET @@time_zone = '+07:00'");

select-data-result.md

SET @@time_zone = 'SYSTEM';
SELECT datetime_value, timestamp_value, inputted_timezone FROM datetime_timestamp ORDER BY id;

datetime_value	timestamp_value	inputted_timezone
2020-01-01 10:10:10	2020-01-01 10:10:10	SET @@time_zone = SYSTEM
2020-01-01 10:10:10	2020-01-01 03:10:10	SET @@time_zone = +07:00

SET @@time_zone = '+07:00';
SELECT datetime_value, timestamp_value, inputted_timezone FROM datetime_timestamp ORDER BY id;

datetime_value	timestamp_value	inputted_timezone
2020-01-01 10:10:10	2020-01-01 17:10:10	SET @@time_zone = SYSTEM
2020-01-01 10:10:10	2020-01-01 10:10:10	SET @@time_zone = +07:00

select-data.sql

# Select data
SET @@time_zone = 'SYSTEM';
SELECT "SET @@time_zone = 'SYSTEM' before select", datetime_value, timestamp_value, inputted_timezone FROM datetime_timestamp ORDER BY id;

SET @@time_zone = '+07:00';
SELECT "SET @@time_zone = '+07:00' before select", datetime_value, timestamp_value, inputted_timezone FROM datetime_timestamp ORDER BY id;