//Query warning eror
SELECT TABHDBHCT.MAVACH_SP, TABHDBHCT.TENSP, SUM(TABHDBHCT.SOLUONG)*CASE WHEN [TRAHANG] = 0 THEN 1 ELSE -1 END AS SL
FROM TABHDBHCT INNER JOIN
     TABHDBH ON TABHDBHCT.MASOPHIEU = TABHDBH.IDSOPHIEU
WHERE (TABHDBH.TTTHANHTOAN = 1 OR
      TABHDBH.TTTHANHTOAN = 2) AND (TABHDBH.NGAY BETWEEN '11/01/2016' AND '11/30/2016')
GROUP BY TABHDBHCT.MAVACH_SP, TABHDBHCT.TENSP
ORDER BY TABHDBHCT.TENSP;