这样:
DM.IBQuery1.Active:=false;
DM.IBQuery1.SQL.Clear;
DM.IBQuery1.Params.Clear;
DM.IBQuery1.SQL.Add('select min(dm) from dm_clb where mc=''' + EdtClmc.Text + ''' ');
DM.IBQuery1.Active:=true;
if not DM.IBQuery1.Eof then
cldm :=DM.IBQuery1.Fields.Fields[0].AsString;