not allowed to return a resultset from a trigger mysql

Question

delimiter $$
CREATE TRIGGER REDUCE_NOTE_COUNT
 AFTER DELETE ON iv_notes
 FOR EACH ROW  BEGIN
DECLARE supplierid int(11);
DECLARE customerid int(11);

SELECT supplier         


        

Answer 1

You cannot execute SELECT statements from trigger. If you want to set variables, then use SELECT INTO statement, e.g. -

DECLARE supplierid_ INT(11);
DECLARE customerid_ INT(11);

SELECT
  supplierid, customerid
INTO
  supplierid_, customerid_
FROM
  iv_documents
WHERE
  id = OLD.note_documentid;

IF supplierid_ = OLD.note_companyid THEN
...

Also, rename variables, they have to differ from from field names.