MySQL COALESCE Function Returns When All Arguments 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)