CREATE TRIGGER CHANGEDINVOICEINS AFTER INSERT ON vp_invoicelines FOR EACH ROW
BEGIN
    DECLARE fullamount INT DEFAULT 0;
    DECLARE invoicescount INT DEFAULT 0;
    SELECT SUM(COUNT*price) INTO fullamount FROM vp_invoicelines WHERE invoicenumber=NEW.invoicenumber;
    SELECT COUNT(*) INTO invoicescount FROM vp_invoiceheader WHERE id=NEW.invoicenumber;
    IF(invoicescount=0) THEN
        INSERT INTO vp_invoiceheader (provider,customer,releasedate,amount) VALUES ("ProviderX","CustomerX","2015-11-29",fullamount);
    ELSE
        UPDATE vp_invoiceheader SET amount=fullamount WHERE id=NEW.invoicenumber;
    END IF;
END;


CREATE TRIGGER CHANGEDINVOICEUPD AFTER UPDATE ON vp_invoicelines FOR EACH ROW
BEGIN
    DECLARE fullamount INT;
    SELECT SUM(COUNT*price) INTO fullamount FROM vp_invoicelines WHERE invoicenumber=NEW.invoicenumber;
    UPDATE vp_invoiceheader SET amount=fullamount WHERE  id=NEW.invoicenumber;
END;


CREATE TRIGGER CHANGEDINVOICEDEL AFTER DELETE ON vp_invoicelines FOR EACH ROW
BEGIN
    DECLARE fullamount INT;
    DECLARE invoicescount INT;
    SELECT SUM(COUNT*price) INTO fullamount FROM vp_invoicelines WHERE invoicenumber=OLD.invoicenumber;
    SELECT COUNT(*) INTO invoicescount FROM vp_invoiceheader WHERE id=OLD.invoicenumber;
    IF(invoicescount=1) THEN
        DELETE FROM vp_invoiceheader WHERE id=OLD.invoicenumber;
    END IF;
    IF(invoicescount>1) THEN
        UPDATE vp_invoiceheader SET amount=fullamount WHERE  id=OLD.invoicenumber;
    END IF;
END;