List the names of all the universities that have no less than 50,000 students in the year 2012.
have no less than 50,000 students refers to num_students > 50000; name of university refers to university_name;
SELECT T2.university_name FROM university_year AS T1 INNER JOIN university AS T2 ON T1.university_id = T2.id WHERE T1.num_students > 50000 AND T1.year = 2012