It may happen in rare cases that Piwik believes it has upgraded to a newer version, but that the database itself was not actually upgraded. This FAQ explains how to re-run the database upgrade from a particular version.
For example, this could happen if the database crashed or overloaded during the DB upgrade (we recommend to enable maintenance and run the ugprade in the command line). It could also happen if the new Piwik files in core/Updates/ haven’t yet been uploaded to the latest files, but a Piwik user visits the Piwik UI and issues the partial upgrade leading to the errors.
As a result SQL error messages are often printed in some – or all – the reports. Errors messages such as
Error trying to execute the query 'CREATE TABLE [...] Base table or view already exists: 1050 Table exists
SQLSTATE[42S22]: Column not found: 1054 Unknown column on clause
SQLSTATE: Syntax error or access violation: 1091 Can't DROP X check that column/key exist
Error trying to execute the query 'ALTER TABLE' SQLSTATE[42S22]: Column not found: 1054 Unknown column
Error in Piwik (tracker): Error query: fetch() failed: Unknown column '...' in 'field list'
The good news is that it possible in all cases to resolve the issue and not experience any data loss or other problem!
You can manually tell Piwik to run the upgrade again by executing the following SQL query (eg. using a tool such as phpMyAdmin):
UPDATE `piwik_option` SET option_value = "1.X" WHERE option_name = "version_core";
Replace 1.X with the version you were using prior to upgrading, for example “1.10”. After running this query, visit Piwik: you should see the upgrade screen again. You can run the upgrade in the command line if your Piwik is large, or simply click the button and wait until completion.
If you still have problems, you can get help in the forums or contact Professional Services for paid support by world leading Piwik experts.