Query For Empty Tax Code

SELECT H.D_ate, D.RunNo, D.ItemCode, D.Description, D.Qty, D.HCUnitCost, D.HCTax, ((6/106)*D.HCLineAmt) as vHCTax, D.HCLineAmt, D.DetailTaxCode, D.TaxRate1 FROM stk_cus_inv_dt D INNER JOIN stk_cus_inv_hd H ON D.Doc1No = H.Doc1No WHERE H.D_ate BETWEEN '2016/04/01' AND '2016/04/30' AND D.DetailTaxCode = ''