CREATE TABLE files (f_id VARCHAR2, formats VARCHAR2, resolution NUMBER)
CREATE TABLE song (f_id VARCHAR2, formats VARCHAR2, resolution NUMBER)

What are the ids of songs that are available in either mp4 format or have resolution above 720?
SELECT f_id FROM files WHERE formats = "mp4" UNION SELECT f_id FROM song WHERE resolution > 720
SELECT "f_id" FROM "files" WHERE "formats" = "mp4" UNION SELECT "f_id" FROM "song" WHERE "resolution" > 720