CREATE TABLE table_21330550_2 (date VARCHAR2, big_ten_team VARCHAR2)

How many dates have a big ten team of #10 purdue?
SELECT COUNT(date) FROM table_21330550_2 WHERE big_ten_team = "#10 Purdue"
SELECT COUNT("date") FROM "table_21330550_2" WHERE "#10 Purdue" = "big_ten_team"