Actually, CONCAT_WS() function returns NULL if and only if the first argument of it i.e. the separator is NULL. An example is as below −
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 ignores NULL if we place NULL at any other position in CONCAT_WS() function while linking the strings. Following examples will exhibit 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)