A WordPress install uses a database to set up tables. Version 1.2.2 has its own stable structure, and, by default, each table has the name of wp_tablename. This is set in the
All of your posts, comments, settings and such are held in those tables. If you wish to install another version of WordPress, you need to install it in a different directory, and in that installation, you can use the same database, except that the new version will have its own table structure. In the
wp-config.php of your new install you will have to define a new table prefix name. Instead of
wp_ you can give it anything else that you would like. For example, you could call it
wp15_ so that you version 1.5 install would have all of its tables identified/called/labelled/entitled as
These two installs will NOT share the same posts, comments and other settings. They are separate and distinct installs, and your new install will have only the default first post and first comment.
There are ways to copy over your comments and posts, but I won't get into that here, other than to say that this doesn't integrate the tables, rather it creates a copy which would have to be constantly maintained should you wish to run identical comment on blogs powered by two different versions of WordPress.
Remember that a database is simply a container which holds tables. WordPress can be set up to create unique tables for each version you wish to run, so different versions can live happily next to each other in the same database.