WordPress database error: [Can’t create table … (errno: 121)]

I was trying to upgrade one of my test blogs to WordPress 2.3 RC1 when I got error messages like the above littering the screen during the installation. The PHP functions mysql_noerr (or mysqli_noerr) and mysql_error (or mysqli_error) seem to have been busily at work. These messages told me that the upgrade hadn’t worked so I went off googling as usual and perusing the MySQL tomes in my possession. Not for the first time, the web yielded nothing but dross and, in the end, I tried deleting the relevant database and starting from scratch again. That resolved the problem.

The reason for database deletion sorting things out is that MySQL got confused when there was a mismatch between what was in the file system and what its InnoDB table was saying. I think that the cause of this was that I naively copied in tables using Windows Explorer. Deleting the database cleared the air and all was well once I allowed WordPress to do the needful in its time honoured way. Another lesson learned for the future and I wish that frustration wasn’t part of the learning experience too…