Table: bitburger_open_tennis
Columns: year
mens_singles
womens_singles
mens_doubles
womens_doubles
mixed_doubles

Question: When did Chetan Anand win his first men's single?
SQL: SELECT MIN("year") FROM bitburger_open_tennis WHERE "mens_singles" = 'Chetan Anand'

Question: How many times did Niels Christian Kaldau win the men's single and Pi Hongyan win the women's single in the same year?
SQL: SELECT COUNT("year") FROM bitburger_open_tennis WHERE "mens_singles" = 'Niels Christian Kaldau' AND "womens_singles" = 'Pi Hongyan'

Question: Who won the men's double when Chou Tien-Chen won the men's single?
SQL: SELECT "mens_doubles" FROM bitburger_open_tennis WHERE "mens_singles" = 'Chou Tien-chen'