Простой пример работы с базой данных из DLL

library Mydll;

uses
  DBTables;

function Modify(Key: Double; const Info: string): Boolean; export;
var
  Table: TTable;
  Stream: TBlobStream;
begin
  Table := TTable.Create(nil);
  Table.DatabaseName := 'D:\';
  Table.TableName := 'BIOLIFE';
  Table.TableType := ttParadox;
  Table.Open;
  if Table.FindKey([Key]) then
  begin
    Result := True;
    Table.Edit;
    Stream := TBlobStream.Create(TMemoField(Table.FieldByName('Notes')),
      bmReadWrite);
    Stream.Seek(0, 2);
    Stream.Write(Info[1], Length(Info));
    Stream.Free;
    Table.Post;
  end
  else
    Result := False;
  Table.Free;
end;

exports
  Modify;

begin
end.

function Modify(Key: Double; const Info: String): Boolean; far;
external 'MYDLL';
...
// Modify(90200, 'Васек Трубачев');