Modify
======

This is command which does change the contents of
the underlying data source.

This is a subclass of the command class.

Attributes
==========

   State      - Open/Closed
   Num_Params - Number of parameter marks (?) in the sql statement,
                available if State = Open

Methods
=======
   Open      - Initiate instance
   Close     - Release resources
   Execute   - Execute the modification command. Returns the number
               of inserted/updated or deleted rows.
   Set       - Set the parameter value n

Interfaces
==========

Example
======= 

  con      : Connection.Instance;
  cmd      : Modifier.Handle;

  X        : Integer := 1;
  Y        : Integer := 2;
  Result   : Natural;
begin

  Connection.Open (con, "......");

  cmd := Modify.Open (con, "INSERT INTO XYZ VALUES (?, ?)");

  Parameter (cmd, 1, X);  -- Sets the address for param 1
  Parameter (cmd, 2, Y);  -- Sets the address for param 2

  Result := Execute (cmd);
  Close (Cmd);
  Connection.Commit (Con);

  Modifier.Open (cmd, con, "INSERT INTO XYZ VALUES (?, ?)");

  Modifier.Set (Cmd, 1, X)       -- Sets the value 
  Modifier.Set (Cmd, 2, Y);
  Result := Execute (cmd);

  Modifier.Set (Cmd, 1, 1234);   -- Sets the value 
  Modify.Set (Cmd, 2, 5678);
  Result := Execute (Cmd);
  Close (Cmd);

  Connection.Commit (Con)
  Close (Con);

end ;


