Question

I am trying to bring together two separate designs here so I understand the overall approach may not be ideal. Basically through user input in PHP table1 and part of table2 is populated and then in turn I need the rest of table2 and table3 to be populated automatically.

I have the following db

with this trigger

DELIMITER |

CREATE TRIGGER new_trigger AFTER INSERT on table2
FOR EACH ROW BEGIN
    INSERT INTO table3(att1, DateCreated, DateUpdated)
    VALUES('PG', now(), now());
    UPDATE table2 SET table3Id = table3.LAST_INSERT_ID();
END;
|

DELIMITER ;

although MySQL accepts the trigger as written without any errors I get this error when the app runs:

 General error: 1442 Can't update table 'table2' in stored function/trigger 
    because it is already used by statement which invoked this stored function/trigger

I believe this comes from MySQL triggers can’t manipulate the table they are assigned to. So if this is the reason for the error how else can I achieve the same results?

EDIT: (ANSWER)

Thanks to the help from mootinator here and in chat. Here is his solution that works as I need it to.

CREATE TRIGGER new_trigger BEFORE INSERT on table2
FOR EACH ROW BEGIN
    INSERT INTO table3(att1, DateCreated, DateUpdated)
    VALUES('PG', now(), now());
    SET NEW.table3Id = LAST_INSERT_ID();
END;

Answer 1

You can’t use an AFTER trigger because the new change you make would (potentially) cause the AFTER trigger to be run again in an infinite loop. You have to use a BEFORE trigger to edit the row before it gets written.

Try eg:

CREATE TRIGGER new_trigger BEFORE INSERT on table2
FOR EACH ROW BEGIN
    INSERT INTO table3(att1, DateCreated, DateUpdated)
    VALUES('PG', now(), now());
    SET NEW.table3Id = LAST_INSERT_ID();
END;