We have a site on magento 1.7 that I want to upgrade to 1.9 with a new theme.
In the live site (1.7) have probably been changes in the core (it is created by other).
We think to do a clean install magento 1.9 and put there the new theme and then we import / override tables associated with the products / categories / orders / users etc and exclude tables related with blocks, cms pages etc to avoid losing changes / additions have been made to the new theme.
is that logic correct? do you suggest something else? How to separate what tables relates only to the theme (and must be not replaced) ?
Just copy and paste magento 1.9.1 files to your magento store root.
First of all, please take the backup of your store files and reload the home page.