รบกวนสอบถามเกี่ยวกับคำสั่ง SQL ขึ้น error ช่วยชี้แนะให้ผมทีครับ

SELECT tb_item.Item_id,tb_item.Item_code,tb_item.Item_detail,tb_item.Item_price,tb_item.Item_unit,tb_category.Cate_name,SUM(Redetail_amount) as qty,
(SELECT tb_item.Item_id,SUM(tb_receivedetail.Redetail_amount) FROM tb_receivedetail INNER JOIN tb_receive ON tb_receivedetail.Receive_id = tb_receive.Receive_id WHERE MONTH(Get_date) = '9' AND YEAR(Get_date) <= '2018') AS qty_2
                    FROM tb_receivedetail
                    INNER JOIN tb_receive ON tb_receivedetail.Receive_id = tb_receive.Receive_id
                    INNER JOIN tb_item ON tb_receivedetail.Item_id = tb_item.Item_id
                    INNER JOIN tb_category ON tb_item.Cate_id = tb_category.Cate_id
                    WHERE MONTH(Get_date) < '9' AND YEAR(Get_date) <= '2018'
                    GROUP BY Item_id

Error operand 
Check " >, >=, <,<=, +,-,*,/       "

WHERE MONTH(Get_date) = '9' AND YEAR(Get_date) <= '2018') AS qty_2

(SELECT tb_item.Item_id,SUM(tb_receivedetail.Redetail_amount) FROM tb_receivedetail INNER JOIN tb_receive ON tb_receivedetail.Receive_id = tb_receive.Receive_id WHERE MONTH(Get_date) = '9' AND YEAR(Get_date) <= '2018') AS qty_2

SELECT tb_item.Item_id,tb_item.Item_code,tb_item.Item_detail,tb_item.Item_price,tb_item.Item_unit,tb_category.Cate_name,SUM(Redetail_amount) as qty,(SELECT SUM(Redetail_amount) FROM tb_receivedetail INNER JOIN tb_receive ON tb_receivedetail.Receive_id = tb_receive.Receive_id  WHERE MONTH(Get_date) = '9' AND YEAR(Get_date) <= '2018' GROUP BY Item_id) AS qty_2
                    FROM tb_receivedetail
                    INNER JOIN tb_receive ON tb_receivedetail.Receive_id = tb_receive.Receive_id
                    INNER JOIN tb_item ON tb_receivedetail.Item_id = tb_item.Item_id
                    INNER JOIN tb_category ON tb_item.Cate_id = tb_category.Cate_id
                    WHERE MONTH(Get_date) < '9' AND YEAR(Get_date) <= '2018'
                    GROUP BY Item_id

SELECT tb.Item_id,tb.Item_code,tb.Item_detail,tb.Item_price,tb.Item_unit
, ct.Cate_name, SUM(rd.Redetail_amount) as qty, (
   select sum(dt.redetail_amount) from tb_receivedetail dt, tb_receive cv
   where dt.Receive_id = cv.Receive_id 
   and MONTH(cv.Get_date) < '9' AND YEAR(cv.Get_date) <= '2018'
   and dt.item_id=tb.item_id
) as qty2
FROM tb_receivedetail rd, tb_receive rc, tb_item tb, tb_category ct
where rd.Receive_id = rc.Receive_id
and rd.Item_id = tb.Item_id
and tb.Cate_id = ct.Cate_id
and MONTH(rc.Get_date) < '9' AND YEAR(rc.Get_date) <= '2018'
GROUP BY tb.Item_id