Didn’t even open the link probably

That’s a fair point, I guess I used binary numbers so much i uni that I just know the small ones by heart and that’s why I find it easier. Following the example, I never convert 101 as 4+0+1, I just see it and know it’s 5.

Read, write, and execute are represented by the numbers 4, 2, and 1, respectively, and you add them together to get the permission

Maybe I’m the weird one here but this seems like a counter intuitive way to remeber/explain it. Each octal digit in the three digit number is actually just 3 binary digits ( 3 bit flags) in order of rwx. For example read and execute would be 101 -> 5.

At the (SQL) database level, if you are using null in any sane way, it means “this value exists but is unknown”.

Null at the SQL means that the value isn’t there, idk where you’re getting that from. SQL doesn’t have anything like JS’s undefined, there’s no other way to represent a missing value in sql other than null (you could technically decide on certain values for certain types, like an empty string, but that’s not something SQL defines).