CONCAT() and RTRIM() both return NULL if any of their arguments are NULL. So CONCAT(‘xyz’, NULL) returns NULL. RTRIM(NULL) returns NULL. CONCAT(‘xyz’, NULL, ‘123’) returns NULL. coalesce(FIELD, ‘—‘)
Attention in classroom
CONCAT() and RTRIM() both return NULL if any of their arguments are NULL. So CONCAT(‘xyz’, NULL) returns NULL. RTRIM(NULL) returns NULL. CONCAT(‘xyz’, NULL, ‘123’) returns NULL. coalesce(FIELD, ‘—‘)