CREATE TABLE table_name_17 (constructor VARCHAR, circuit VARCHAR, date VARCHAR)

What company constrcuted the vehicle with a circuit of oulton park on 15 april?
SELECT constructor FROM table_name_17 WHERE circuit = "oulton park" AND date = "15 april"
SELECT "constructor" FROM "table_name_17" WHERE "15 april" = "date" AND "circuit" = "oulton park"