While concatenating strings, if I add NULL values, what is the output of CONCAT_WS() function?

In fact, the CONCAT_WS() function returns NULL if and only if its first parameter (i.e., the delimiter) is NULL. An example is as follows -

mysql> Select CONCAT_ws(NULL,'Tutorial','Point','.com');
+-------------------------------------------+
| CONCAT_ws(NULL,'Tutorial','Point','.com') |
+-------------------------------------------+
| NULL                                      |
+-------------------------------------------+
1 row in set (0.00 sec)

Otherwise, MySQL CONCAT_WS() function will ignore NULL if we place NULL anywhere else in CONCAT_WS() function while concatenating strings. The following example will demonstrate it -

mysql> Select CONCAT_ws('s','Tutorial','Point','.com',NULL);
+-----------------------------------------------+
| CONCAT_ws('s','Tutorial','Point','.com',NULL) |
+-----------------------------------------------+
| TutorialsPoints.com                           |
+-----------------------------------------------+
1 row in set (0.00 sec)

mysql> Select CONCAT_ws('s','Tutorial',NULL,'Point','.com');
+-----------------------------------------------+
| CONCAT_ws('s','Tutorial',NULL,'Point','.com') |
+-----------------------------------------------+
| TutorialsPoints.com                           |
+-----------------------------------------------+
1 row in set (0.00 sec)

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