If you look at the description for the different tables used by WordPress, the columns described as “auto_increment” will be unique.
I am not sure what you are doing though. The URL structure you are using is not one that I recognize. That is, the syntax I think you want is this:
example.com/?p=1774
rather than this:
example.com/?id=1774
?p= + a valid ID should always give you the post with the referenced ID number.