Avoid firing trigger by another trigger in MYSQL - mysql

Question

my problem is as follows:
Table A contains list of "Tasks"
Table B contains "TaskProgress" - just an information about time spent on task, user ID, task ID and note
On table A (Tasks), I have trigger, which updates datetime of last change - column DateChanged (intended to capture datetime of edits made by user)
On table B (TaskProgress) I have trigger, which updates total time spent on a task (sum all times for given Task_ID and update column TotalTime in table A)
I wish to update DateChanged in Table A only when user mades the update (which is every time except when trigger on table B updates TotalTime)
So I wonder, whether there is a way how to tell the database not to fire TRIGGER when updating the values in another trigger.
/* set date of last change and date od closing of task */
DELIMITER $$
CREATE TRIGGER before_tasks_update
BEFORE UPDATE ON tasks
FOR EACH ROW BEGIN
SET new.DateChanged = NOW();
IF new.Status_ID = 3 THEN
SET new.DateClosed = NOW();
END IF;
END$$
DELIMITER ;
/* set total time spent on task */
DELIMITER $$
CREATE TRIGGER after_taskprogress_insert
AFTER INSERT ON taskprogress
FOR EACH ROW BEGIN
DECLARE sumtime TIME;
SET #sumtime := (SELECT SEC_TO_TIME( SUM( TIME_TO_SEC( `timeSpent` ) ) )
FROM taskprogress WHERE Task_ID = new.Task_ID);
UPDATE `tasks` SET TimeReal = #sumtime WHERE ID = new.Task_ID;
END $$
DELIMITER ;
I use MySQL 5.5.40
Thanks, zbynek

Answer 1

Add a check to verify that the update implies a new TimeReal value,since only the second trigger updates that column.
DELIMITER $$
CREATE TRIGGER before_tasks_update
BEFORE UPDATE ON tasks
FOR EACH ROW BEGIN
IF new.TimeReal=old.TimeReal THEN SET new.DateChanged = NOW();
END IF;
IF new.TimeReal=old.TimeReal AND new.Status_ID = 3 THEN
SET new.DateClosed = NOW();
END IF;
END$$
DELIMITER ;