Harken back to elementary school days.
What is the value of
If you said 14, go back to sixth grade.
Multiplication has higher *precedence* than addition, so the answer is 11. (Multiply 4 times 2 first *then* add 3.)
Same with AND and OR in all computer languages.
If you wanted 14 as the answer, you needed to write
OR is like +
AND is like *
When you do
you are, effectively, writing
a or b or ( c and d )
So, as Dan said, you need to explicitly use the parentheses:
( a or b or c ) and d
Oh, and MySQL allows *either* <> or != and treats them 100% the same.