01-31', 1) |
+-----------------------------+
| 2011-02-28                  |
+-----------------------------+

SELECT ADD_MONTHS('2012-01-31', 1);
+-----------------------------+
| ADD_MONTHS('2012-01-31', 1) |
+-----------------------------+
| 2012-02-29                  |
+-----------------------------+

SELECT ADD_MONTHS('2012-01-31', 2);
+-----------------------------+
| ADD_MONTHS('2012-01-31', 2) |
+-----------------------------+
| 2012-03-31                  |
+-----------------------------+

SELECT ADD_MONTHS('2012-01-31', 3);
+-----------------------------+
| ADD_MONTHS('2012-01-31', 3) |
+-----------------------------+
| 2012-04-30                  |
+-----------------------------+

SELECT ADD_MONTHS('2011-01-15', 2.5);
+-------------------------------+
| ADD_MONTHS('2011-01-15', 2.5) |
+-------------------------------+
| 2011-04-15                    |
+-------------------------------+
1 row in set (0.001 sec)

SELECT ADD_MONTHS('2011-01-15', 2.6);
+-------------------------------+
| ADD_MONTHS('2011-01-15', 2.6) |
+-------------------------------+
| 2011-04-15                    |
+-------------------------------+
1 row in set (0.001 sec)

SELECT ADD_MONTHS('2011-01-15', 2.1);
+-------------------------------+
| ADD_MONTHS('2011-01-15', 2.1) |
+-------------------------------+
| 2011-03-15                    |
+-------------------------------+
1 row in set (0.004 sec)

URL: https://mariadb.com/kb/en/add_months/https://mariadb.com/kb/en/add_months/