Question

I’m newbie with Triggers, but I’m think that I need code one for my case:

CREATE TABLE `events` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `device_id` varchar(15) DEFAULT NULL,
  `event_type` varchar(15) DEFAULT NULL,
  `event_value` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4987 DEFAULT CHARSET=utf8$$

CREATE TABLE `sequence` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `device_id` varchar(15) DEFAULT NULL,
  `values_sum` varchar(15) DEFAULT NULL,
  `event_value` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4987 DEFAULT CHARSET=utf8$$

I need when is inserted a row of events table, check if the event_type is 1 or 2

If 1 I need copy in the second table the first data and add every 1 event until
the next insert the event_type will be 2..

I don’t know how do that, any help are welcome…

Answer 1

Here’s some sample syntax that will help get you started.

You’ll need to figure out what you are going to store in the values_sum column of the sequence table.

Also, the trigger below is copying the id value from the events table into the sequence table, and that is going to be a problem (i.e. duplicate key exception) if some other process inserts and generates new id values in the sequence table.

DELIMITER $$

CREATE TRIGGER `trg_events_ai` 
  AFTER INSERT ON `events`
  FOR EACH ROW
  BEGIN
    IF NEW.event_type = 1 THEN
      INSERT INTO `sequence` (`id`, `device_id`, `values_sum`, `event_value`)
      VALUES NEW.id, NEW.device_id, NULL, NEW.event_value);
    END IF;
  END$$

DELIMITER ;

This example trigger will be “fired” after an insert to the events table. For any row inserted to the events table where the event_type column is a 1, then this trigger will issue a corresponding INSERT against the sequence table. Should be enough to get you started.