num
    ---
    2
    2
    2
    2
    3
    3

id  | users
    ------------
    1   | Jhon
    2   | Jimmy
    3   | Michael
    4   | Simon
    5   | Tom

SELECT users
FROM table_2 a
     INNER JOIN (SELECT DISTINCT num FROM table_1) b
         ON a.id = b.num;

SELECT users
FROM table_2 a
     INNER JOIN (SELECT num FROM table_1 group by num) b
         ON a.id = b.num