CREATE TABLE table_name_4 (fastest_lap VARCHAR2, winning_driver VARCHAR2, date VARCHAR2)

Who had the fastest lap of the race that Ayrton Senna won on 23 April?
SELECT fastest_lap FROM table_name_4 WHERE winning_driver = "ayrton senna" AND date = "23 april"
SELECT "fastest_lap" FROM "table_name_4" WHERE "23 april" = "date" AND "ayrton senna" = "winning_driver"