[1.2.X] Fixed small multi-db compatibility issue in the Oracle backend.

Also, converted a couple of constructs to a more Python idiomatic form.

Backport of [14512] from trunk

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14513 bcc190cf-cafb-0310-a4f2-bffc1f526a37