CREATE TABLE table_37438 ("Race" TEXT, "Length" TEXT, "Class" TEXT, "Circuit" TEXT, "Date" TEXT)

Which circuit has a length of 45 minutes and is held on August 6?
SELECT "Circuit" FROM table_37438 WHERE "Length" = '45 minutes' AND "Date" = 'august 6'
SELECT "Circuit" FROM "table_37438" WHERE "Date" = 'august 6' AND "Length" = '45 minutes'