Trigger for moving a few records to another table

[Marek Zima]

Hi, I have a table message and message_archive and I want to move a few records (500) to message_archive when the count of the records with the same column group_id is the same...

CREATE TRIGGER after_message_update
AFTER INSERT ON message
FOR EACH ROW
BEGIN
DECLARE count_messages integer
DECLARE id_messages integer

SET count_messages = (SELECT COUNT(id) FROM message WHERE message_group_id IN (SELECT id FROM message));
SET id_messages = (SELECT id FROM message WHERE message_group_id IN (SELECT id FROM message));

insert into message_archive
select * from message where count_messages > 2;
delete from message where message_group_id IN id_messages;
END

does somebody help me?