Database: wta_1
Question: What are the first names and country codes for players who won both the WTA Championships and the 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'