What MySQL Returns If Search String in FIELD Function is NULL

As we know that NULL fails equality comparison with any value hence if the search string, provided in FIELD() function, is NULL then MySQL returns 0 as output.

Example

mysql> Select FIELD(NULL,'Ram','is','good','boy');

+-------------------------------------+
| FIELD(NULL,'Ram','is','good','boy') |
+-------------------------------------+
|                                   0 |
+-------------------------------------+

1 row in set (0.00 sec)