How to find all games between any pair of players belonging to a given list
If you have a list of let's say four players (A,B,C,D) and wish to extract from a large database all games where both opponents are among your four chosen ones, you have no easy solution in databases like SCID or Chessbase : you will have to manually select each possible pair of players and repeat the simple search operation as many times as required.
Having all this performed in one step is easy with PGNextract...
see here
Marc