TRIGGER MYSQL NOT EXIST - mysql

Question

I created this trigger:
CREATE TABLE `Invitations`
( `userId` varchar(255) NOT NULL, `name` varchar(255) DEFAULT NULL,
`status` varchar(1) DEFAULT NULL, `userId_inv` varchar(255) NOT NULL,
PRIMARY KEY (`userId`,`userId_inv`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1
CREATE TRIGGER `Invitation_001_after_trig` AFTER INSERT ON `invitation_001`
FOR EACH ROW
BEGIN
IF ((new.userId,'001') NOT EXISTS (SELECT `userId`,`userId_inv` FROM `Invitations`
WHERE `userId`= new.userId AND `userId_inv` = '001' LIMIT 1))
THEN
INSERT INTO `Invitations`(`userId`, `name`,`status`,`userId_inv`)
values (new.userId, new.name,new.status,'001');
DELETE FROM `invitation_001` WHERE `status` = 'a';
END IF;
END;
It did not work. I had this error:
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 'EXISTS (SELECT userId,userId_inv FROM Invitations WHERE
userId= new.user' at line 1
So could you help me.
I resolved the problem with this trigger:
CREATE TRIGGER `Invitation_001_after_trig` AFTER INSERT ON `invitation_001`
FOR EACH ROW
BEGIN
INSERT INTO `Invitations` (`userId`, `name` ,`status` ,`userId_inv`) SELECT * FROM
invitation_001 iv WHERE
NOT EXISTS (SELECT 1 FROM `Invitations` ivs WHERE ivs.`userId` = iv.`userId` AND
ivs.`userId_inv` = iv.`userId_inv`) AND iv.`userId_inv`='001';END;
Now I've an other issue. I would like to execute a query from a Concat String in a trigger but until now I did not succeed so here is my code:
CREATE TRIGGER `InvitationS_after_trig` AFTER INSERT ON `Invitations`
FOR EACH ROW
BEGIN
if(new.status ='c' OR new.status ='r')
BEGIN
SET #query = CONCAT("INSERT INTO", Invetations.userId,"values(new.userId,new.name,new.status,new.userId_inv);");
PREPARE stmt1 FROM #query;
EXECUTE stmt1;
DEALLOCATE PREPARE stmt1;
END IF;
END;
I resolved the syntax problem but I now have an other one:
Dynamic SQL is not allowed in stored function or trigger
I'm using MySQL version 5.1.69.
Finally I give up, I will resolve this problem using java Fonction