Triggers can not use reference to tables?

[Chagh]

hi all,
I've got a trigger in MS SQLServer 2000 and i want to migrate it to MySQL. my trigger in SQLServer is:

CREATE TRIGGER AddAttach ON dbo._Attachments FOR INSERT

AS

DECLARE @DocCode int
DECLARE @InsertedCount int

SELECT @DocCode = DocCode , @InsertedCount = Count(*)
FROM    INSERTED
GROUP BY DocCode

UPDATE _Documents SET
  AttachCount = AttachCount + @InsertedCount
WHERE   DocCode = @DocCode

UPDATE _Attachments SET
  RelAttNumber = INSERTED.AttNumber
FROM    INSERTED
WHERE INSERTED.AttachmentCode = _Attachments.AttachmentCode

I know we can not reference to tables in triggers(like functions), so what should i do?
(when i execute this "create trigger ..." statement in MySQL by the code below it gives me syntax error:

CREATE TRIGGER AddAttach after INSERT ON _Attachments for each row

begin

DECLARE DocCode int;
DECLARE InsertedCount int;

SELECT  DocCode , Count(*) into DocCode,  InsertedCount
FROM    INSERTED
GROUP BY DocCode;

UPDATE _Documents SET
  AttachCount = AttachCount + InsertedCount
WHERE   DocCode = DocCode;

UPDATE _Attachments SET
  RelAttNumber = INSERTED.AttNumber
FROM    INSERTED
WHERE INSERTED.AttachmentCode = _Attachments.AttachmentCode;

end

the error is:
"ERROR 1064 (42000): 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 'UPDAT
E _Attachments SET
RelAttNumber = INSERTED.AttNumber
FROM INSERTED
WHE' at line 7"
)