MySQL MONTHNAME() from numbers

You can use STR_TO_DATE() to convert the number to a date, and then back with MONTHNAME()

SELECT MONTHNAME(STR_TO_DATE(6, '%m'));

+---------------------------------+
| MONTHNAME(STR_TO_DATE(6, '%m')) |
+---------------------------------+
| June                            |
+---------------------------------+

Warning: This could be slow if done over a lot of rows.