SQL : Database ‘Database_Name’ already exists

SQL : Database ‘Database_Name’ already exists

When re-attaching a database I received an error “Database ‘Database_Name’ already exists.” There were no duplicate name databases with the instance, so this was incorrect.

After running the following SQL I found that the database was still ‘known:’
select name from sys.databases

To resolve the issue, execute the command below, changingt he database name:
DROP database ‘Database_Name’