CREATE TABLE table_23649244_1 (level VARCHAR, artist_1 VARCHAR, artist_2 VARCHAR)

Which level has marvin gaye as artist 1 and david bowie as artist 2?
SELECT level FROM table_23649244_1 WHERE artist_1 = "Marvin Gaye" AND artist_2 = "David Bowie"
SELECT "level" FROM "table_23649244_1" WHERE "David Bowie" = "artist_2" AND "Marvin Gaye" = "artist_1"