plsql not equal

1SELECT 1 FROM dual
2WHERE 1 != 2
3OR    1 <> 2;
4-- WARNING: the not equal operators do NOT check for NULL value:
5-- myTable: ID(CHAR) | flag(NUMBER)
6-- 			A			1
7-- 			B			0
8-- 			C			NULL
9
10SELECT ID FROM myTable t
11WHERE t.flag != 1;
12-- returns B
13
14SELECT ID FROM myTable t
15WHERE t.flag != 1 OR t.flag IS NULL;
16-- returns B and C
17
18