CREATE TABLE genre(
	g_name varchar2(20) not null,
	rating varchar2(10),
	most_popular_in varchar2(50),
	primary key(g_name)
)

CREATE TABLE artist(
	artist_name varchar2(50) not null,
	country varchar2(20),
	gender varchar2(20),
	preferred_genre varchar2(50),
	constraint a_name primary key(artist_name),
	foreign key(preferred_genre) references genre(g_name) ON DELETE CASCADE
)

CREATE TABLE files(
	f_id number(10) not null,
	artist_name varchar2(50),
	file_size varchar2(20),
	duration varchar2(20),
	formats varchar2(20),
	primary key(f_id),
	foreign key(artist_name) references artist(artist_name) ON DELETE CASCADE
)

CREATE TABLE song(
	song_name varchar2(50),
	artist_name varchar2(50),
	country varchar2(20),
	f_id number(10),
    	genre_is varchar2(20),
	rating number(10) check(rating>0 and rating<11),
	languages varchar2(20),
	releasedate Date, 
	resolution number(10) not null,
	constraint s_name primary key(song_name),
	foreign key(artist_name) references artist(artist_name) ON DELETE CASCADE,
	foreign key(f_id) references files(f_id) ON DELETE CASCADE,
	foreign key(genre_is) references genre(g_name) ON DELETE CASCADE
)
SELECT formats FROM files GROUP BY formats ORDER BY COUNT (*) DESC LIMIT 1
Find the file format that is used by the most files.