MySQl在插入和更新同一表时触发错误（错误代码：1064）

Question

TRIGGER `dn_name`.`schedule_arrive` AFTER INSERT
    ON `dn_name`.`administration_schedule`
    FOR EACH ROW BEGIN

    DECLARE approx_hr INT(11), update_hr DATETIME;
    SELECT approx_hr FROM `administration_routes` WHERE id = NEW.route_id INTO approx_hr;
    SELECT DATE_ADD(new.depart_time, INTERVAL approx_hr HOUR_MINUTE) INTO update_hr;    
    UPDATE administration_schedule SET arrive_time=approx_hr WHERE id = NEW.id;

END$$

On running insert query, I designed to select approx hour from route table with related id and set that value to approx_hr , increase datetime from new inserted depart time and assign to update_hr and finally update the arrive_time field in trigger enabled same table. But on executing my query, the system show as follows;

Error Code: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ', update_hr datetime; select approx_hr from administration_routes where id =' at line 7

Answer 1

About the NEW.myColumn and OLD.myColumn , you can only use them when using "BEFORE" something. After an insert, you don't have an OLD.myColumn or NEW.myColumn gut a current one. for what you want to do, use "BEFORE INSERT" and change your "SELECT,... SELECT..., UPDATE..." to a simple

SET NEW.arrive_time = DATE_ADD(NEW.depart_time,INTERVAL ...);

Answer 2

Use a before update trigger:

CREATE TRIGGER `dn_name`.`schedule_arrive` BEFORE INSERT
    ON `dn_name`.`administration_schedule`
    FOR EACH ROW
BEGIN
    DECLARE approx_hr INT(11), update_hr DATETIME;

    SELECT approx_hr FROM `administration_routes` WHERE id = NEW.route_id INTO approx_hr;

    SELECT DATE_ADD(new.depart_time, INTERVAL approx_hr HOUR_MINUTE) INTO update_hr; 

    SET NEW.arrive_time = approx_hr;

END$$