DELETE FROM songs WHERE title LIKE '$title'
// What if $title = "%' OR 'a' = 'a"?
DELETE FROM songs WHERE title LIKE '%' OR 'a' = 'a'
// All rows are deleted!
INSERT INTO songs (title, artist) VALUES ('$title','$artist')
// What if $title = "a','b'),('c" and $artist = "d"
INSERT INTO songs (title, artist) VALUES ('a','b'),('c','d')
// Multiple records inserted!