左联接使用5个表值的总和和负

Question

我正在尝试使用左联接对5个表进行求和和减法运算，但是数量在该函数中自动增加了

    SELECT item.*, SUM(IFNULL(item.item_quantity,0) + 
IFNULL(inward.passedquantity,0) + IFNULL(op.opening_stock,0) -
               IFNULL(bom.quantitytopick,0) + IFNULL(adj.adjustment_quantity,0) 
) as totalquality FROM itemmaster item    
                  LEFT JOIN inwardmaster inward on item.item_barcode = inward.item_barcode
               LEFT JOIN openingstock op on item.item_barcode = op.item_barcode 
                     LEFT JOIN bomupload bom on item.item_barcode = bom.item_barcode
                      left JOIN adjustment_inventory adj on item.item_barcode = adj.item_barcode 
                      GROUP BY item.item_barcode