MySQL, <> clause and OR logic

Beginning SQL learner here. I have the following database ‘drink_name’ with drinks (taken from Head First SQL):

| Blackthorn       |
| Blue Moon        |
| Oh My Gosh       |
| Lime Fizz        |
| Kiss on the Lips |
| Hot Gold         |
| Lone Tree        |
| Greyhound        |
| Indian Summer    |
| Bull Frog        |
| Soda and It      |

This is the ‘drink_name’ column. Then I have another column with ‘main’ ingredients. Among them soda, iced water, etc etc.

I’m playing around and I came upon the following query:

SELECT drink_name FROM easy_drinks WHERE main <> 'soda' OR main <> 'iced tea';

And I’m trying to understand why this query returns EVERY entry. What’s the logic behind this? I know if I wanted to have only the ones without those ingredients I can use AND, and then only the ones without soda or iced tea would come up, but this one I’m puzzled about.
Thanks.

>Solution :

This has not much to do with SQL, it’s simple boolean logic: your condition is always true. The same way that x <> 1 OR x <> 0 is true for any number, main <> 'soda' OR main <> 'iced tea' will be true for any value of main.

Or maybe you didn’t know that WHERE TRUE returns every entry in SQL?