database - Missing data column that doesn't -

forgive me if asking silly question can't figure out wrong

in save button, update datatables database

        {         new sqlcommandbuilder(sa);         sa.update(dtpurchaseproductexp);          new sqlcommandbuilder(sa1);         sa1.update(dtpurchaseproduct);         } 

i don't have 'unit' columns in dtpurchaseproductexp following error shows