1. Examples

CREATE TABLE `job` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `status` varchar(15) DEFAULT NULL COMMENT 'Status 1: In progress 2 Completed 3 Failed',
  `create_at` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT 'Creation time',
  `update_at` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT 'modify time',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

2. Explanation

During the insert operation, if there is a timestamp field, the property is set to current_ Time stamp, the current system time is inserted regardless of whether the field has a set value

During the update operation, if a timestamp field property is set to   ON UPDATE CURRENT_ When the data is updated, this field will automatically update the time

Note: these two properties can be used in combination