this is working perfect
DELIMITER
CREATE TRIGGER `after_update_debt_defaulters` AFTER UPDATE ON `defaulters`
FOR EACH ROW BEGIN
IF ( EXISTS (
SELECT DISTINCT `KRAPIN` FROM defaulters WHERE defaulters.Debt_Amount = '0'
)
)
THEN
UPDATE users
SET users.debtor = '0'
WHERE KRAPIN = NEW.KRAPIN;
END IF;
END