Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE matches (winner_name VARCHAR, tourney_name VARCHAR, winner_hand VARCHAR)

### Question ###
How many different winners both participated in the WTA Championships and were left handed?

### Accurate SQL ###

SELECT COUNT(DISTINCT winner_name) FROM matches WHERE tourney_name = 'WTA Championships' AND winner_hand = 'L'