Jooma - Upgrade 1.7 to 2.5 to 3.0

Upgrade

http://docs.joomla.org/J2.5:Upgrading_from_an_existing_version

 

If you are updating to an x.x.0 release (for example, from 1.7.3 to 2.5.0), this will normally be a file like Joomla_2.5.0-Stable-Update_Package.zip. If you are updating within the same release series (for example, 2.5.0 to 2.5.1), then the file will be named something like Joomla_2.5.0_to_2.5.1-Stable-Patch_Package.zip. 

http://joomlacode.org/gf/project/joomla/frs/?action=FrsReleaseBrowse&frs_package_id=6257

At this point, you have three options:

1. Install from URL
2. Install from Directory
3. Upload Package File

Database Errors When Upgrading to 2.5.0

http://docs.joomla.org/Database_Errors_When_Upgrading_to_2.5.0
When upgrading from an earlier, compatible version, to 2.5.0, you may experience a database error such as the following
JInstaller: :Install: Error SQL DB function failed with error number 1060 Duplicate column name 'ordering' SQL=ALTER TABLE `j17_languages` ADD COLUMN `ordering` int(11) NOT NULL default 0 AFTER `published`; SQL = ALTER TABLE `#__languages` ADD COLUMN `ordering` int(11) NOT NULL default 0 AFTER `published`; Files Update: SQL error file DB function failed with error number 1060 Duplicate column name 'ordering' SQL=ALTER TABLE `j17_languages` ADD COLUMN `ordering` int(11) NOT NULL default 0 AFTER `published`; SQL = ALTER TABLE `#__languages` ADD COLUMN `ordering` int(11) NOT NULL default 0 AFTER `published`;"
To fix this issues, go to Extension Manager -> Database then click the fix button. This will attempt to fix any database issues caused by changes in the database structure that occurred between versions.

Should I update from Joomla! 2.5 to 3.x?

http://docs.joomla.org/Joomla_3_FAQ
In most cases, probably not. Joomla 2.5 will continue be supported until December 31st of 2014 and you can update directly to Joomla 3 once it’s tried-and-tested thoroughly by other users. You can even wait until Joomla 3.5 with release scheduled for Spring 2014 and still get a direct upgrade. The only reason you should update is if you need Joomla 3’s features or want to be on the leading edge.