What MySQL COALESCE() function returns if all the arguments provided to it are NULL?

If all the values in MySQL COALESCE() function are NULL then it returns NULL as the output. It means that this function does not find any non-NULL value in the list.

Example

mysql> Select COALESCE(NULL, NULL, NULL, NULL);
+----------------------------------+
| COALESCE(NULL, NULL, NULL, NULL) |
+----------------------------------+
|                             NULL |
+----------------------------------+

1 row in set (0.00 sec)