查询 返回某表中的某一列的值该怎么写啊
我本来想这么写的，但不行啊，大家帮我看看
Function GetValue(SearchField:string;SearchTable:string):Tstrings;
var
   i:integer;
   tempstr:TStrings;
begin
   tempstr:=TStringlist.Create;
   with frmDm.temp do
   begin
         sql.Clear;
         sql.Add('select distinct ：SearchField   from ：SearchTable');
         parameters.ParamByName('SearchField').Value:=SearchField;
         parameters.ParamByName('SearchTable').Value:=SearchTable;
         open;
         for i:=1 to recordcount do
         begin
            tempstr.Add(fieldbyname('SearchField').Value);
            Next;
         end;
         result:=tempstr;
  end;
end;