触发器阻止INSERT

Question

I have a html form that send some data in a database. I just created a trigger that on every people that complete the city field with LA will add the word "HI FROM LA" in a column named tag.

The problem is that after I created this trigger I get an error when I try to submit a form:

#1442 - Can't update table 'users' in stored function/trigger because it is already used by statement which invoked this stored function/trigger. 

The trigger is:

DELIMITER |
CREATE TRIGGER update_tag BEFORE INSERT ON users
        FOR EACH ROW
        BEGIN
            IF (NEW.city= 'LA') THEN
            INSERT INTO users
            SET NEW.tag = 'HI FROM LA';
            END IF;
        END;
|
DELIMITER ;

The insert is done with:

INSERT INTO users(id, name, city) VALUES(23, "John", "LA")

What alternatives do I have to avoid this conflict?

EDITED TRIGGER:

I also created a new table called 'trigger':

DELIMITER |
CREATE TRIGGER update_tag BEFORE INSERT ON users
        FOR EACH ROW
        BEGIN
            IF (NEW.city= 'LA') THEN
            INSERT INTO trigger
            SET NEW.tag = 'HI FROM LA';
            END IF;
        END;
|
DELIMITER ;

With this trigger, I get an error on line 5

Answer 1

You don't need to work with triggers for this.

The trigger you have showed us would even create an endless loop, if it were to work.

Just use your insert query like this:
insert into users set (city, tag) values ('LA', concat('HI FROM ', city));