Unknown column error after upgrade

If you get a message like,

PHP Fatal error: 1054:Unknown column 'c.customers_secret' in 'field list' ...

or

PHP Fatal error: 1054:Unknown column 'o.language_code' in 'field list' ...

What is happening is that one or more of the ALTER TABLE commands in the upgrade process run by zc_install failed, and now a column which is expected to exist does not.

One very common root cause for this issue is a failure running an ALTER TABLE required by an upgrade because the table in question still has old format dates. See the page date standardization for instructions on how to fix this.

Errors like this are reported in debug logs created by the zc_install process. These special debug logs have the prefix zcInstallLog_.

It is less common, but still possible, that a built-in date field (such as products_date_added) has bad data, which causes a failed upgrade.

Note: Once you fix the issue that caused the ALTER TABLE to fail, you will still need to run the original command to add the new field. You may do this in phpMyAdmin or in Admin > Tools > Install SQL Patches. Example:

ALTER TABLE orders ADD language_code char(2) NOT NULL default '';