vsaka operacija, ki vkljucuje NULL je enaka NULL, torej (idalbuma = NUL) ni enako TRUE, ampak je (idalbuma = NULL) enako NULL...
(idalbuma IS NULL) je pravilna uporaba, ce zelis preveriti, ali ima idalbuma vrednost NULL...
BTW, to ti vse pise tam, kjer si rekel, da si bral:
In SQL, the NULL value is never true in comparison to any other value, even NULL. An expression that contains NULL always produces a NULL value unless otherwise indicated in the documentation for the operators and functions involved in the expression. All columns in the following example return NULL:
mysql> SELECT NULL, 1+NULL, CONCAT('Invisible',NULL);