Error DatabaseSchemaObjectExistsException: Table <em class="placeholder">mollom</em> already exists. in DatabaseSchema->createTa

Its your database... The Table is the actual Table in the database. It basically means there is a mismatch in data from your original database file and the one you currently have, but unfortunately it can't overwrite it. You have to actually uninstall the module and all of its required modules, fields, and other components and then delete the table item out of the MySql database then reinstall the module if you need it (unless you know how to rewrite the sql table information that is needed yourself, I'm assuming)...

Thanks SunRhythms, your post helped me a lot. Drupal returned exactly the same DatabaseSchemaObjectExistsException error ja_design mentioned when trying to use the Title module. I couldn't replace the title entity for a field.

I did exactly what you suggest:
- Uninstall the module from the Drupal (in my case Title module) and removed it from my Modules folder
- Launch PhpMyAdmin, find and drop the table mentioned in the error (in my case field_data_title_field and just in case I also dropped the field_revision_title_field too)
- Install the Title module again

Unfortunately, I'm not able to reproduce this error.

This normally should not happen, since you state that you only disabled the module. Disabling a module does not drop the module's database tables, and re-enabling a module does not re-install the module's database tables.

Something else in your site's setup must have gone wrong, unrelated to the Mollom module.

Sometimes uninstalling doesn't work. Unfortunately, in my case, there was a problem with backup-migrate holding on to tables after a new reinstall of the database.. I don't know why it happened but I knew that the tables were still there after I uninstalled the module and still had the error message after reinstall.

Hi @SunRhythms, glad I stumbled across your post,was running into exactly the same issue. There is more about it here On restore, delete tables that didn't exist at time of backup

For privacy concerns I replaced my name/website with generic paths

just clear your cache, it goes.

Confirming that #6 works perfectly, thanks cooldeeponline. May have to repeat this after every error if you have multiple modules involved.

I also got this error when migrating db from server to server. #6 did the trick how ever.

Clearing the entire cache never worked for me; it would always error out before the issue was resolved. However, manually emptying the 'cache_field' table solved my issue with the table already exists warning:

MySQL:

truncate table cache_field;

Drush:

drush sqlq "truncate table cache_field"