CREATE TABLE matches (winner_id VARCHAR(255), tourney_name VARCHAR(255)); CREATE TABLE players (country_code VARCHAR(255), first_name VARCHAR(255), player_id VARCHAR(255))
What are the country code and first name of the players who won in both tourney WTA Championships and Australian Open?
    
SQL: SELECT T1.country_code, T1.first_name FROM players AS T1 JOIN matches AS T2 ON T1.player_id = T2.winner_id WHERE T2.tourney_name = 'WTA Championships' INTERSECT SELECT T1.country_code, T1.first_name FROM players AS T1 JOIN matches AS T2 ON T1.player_id = T2.winner_id WHERE T2.tourney_name = 'Australian Open'