How many years was the opponent petr korda?
CREATE TABLE table_name_21 (year VARCHAR, opponent VARCHAR)
SELECT COUNT(year) FROM table_name_21 WHERE opponent = "petr korda"
### Context: CREATE TABLE table_name_21 (year VARCHAR, opponent VARCHAR) ### Question: How many years was the opponent petr korda? ### Answer: SELECT COUNT(year) FROM table_name_21 WHERE opponent = "petr korda"