PingPongGame | popular game in US | Game Engine library

I'm using a stored procedure to (try to) write to 3 different tables in MYsql to track ping-pong data and show cool statistics.

So I'm a complete noob to MySQL (and StackOverflow) and haven't really done any sort of database language before so all of this is pretty new to me. I'm trying to make a stored procedure that writes ping-pong stats that come from Ignition(I'm fairly certain that Ignition isn't the problem. It's telling me the writes failed so I think it's a problem with my stored procedure).

I currently have one stored procedure that writes to the players table and can add wins, losses, and total games played when a button is pressed. My problem now is that I want to add statistics where I can track the score and who played against who so I could make graphs and stuff.

This stored procedure is supposed to search through the pingpong table to find if the names passed have played against each other before so I can find the corresponding MatchID. If the players haven't played before, then it should create a new row with a new MatchID(This is the key so it should be unique every time). Once I have the MatchID, I can then figure out how many games the players have played against each other before, what the score was, and who beat who and stuff like that.

Here's what I've written and MySQL says it's fine, but obviously it's not working. I know it's not completely finished but I really need some guidance since this is my second time doing anything with MySQL or and database language for that matter and I don't think this should be failing when I test any sort of write.