SQL Search Help

[B R]

I have a table of players and a table called gamePlayers. In this table I have a row for each game (which has gameID) key, and playerID for each player in each game.

I have a player in question, their unique field is playerID

What I want to do is show the a count of other players who've played in the same same game as the player in question.

For example, player 20 in question, player 30 is in 10 games the same as player 20.

how can I do this?