What MySQL MAKE_SET() function returns if there are all NULL at the place of strings?

MySQL MAKE_SET() function will return nothing if there are all NULL at the place of strings. Following example will demonstrate it −

Example

mysql> Select MAKE_SET(2, NULL,NULL,NULL);
+-----------------------------+
| MAKE_SET(2, NULL,NULL,NULL) |
+-----------------------------+
|                             |
+-----------------------------+
1 row in set (0.00 sec)