diff --git a/django/db/backends/creation.py b/django/db/backends/creation.py
index 8cfca3b8503..8f4958867b8 100644
--- a/django/db/backends/creation.py
+++ b/django/db/backends/creation.py
@@ -61,7 +61,7 @@ class BaseDatabaseCreation(object):
             if f.rel:
                 ref_output, pending = self.sql_for_inline_foreign_key_references(f, known_models, style)
                 if pending:
-                    pr = pending_references.setdefault(f.rel.to, []).append((model, f))
+                    pending_references.setdefault(f.rel.to, []).append((model, f))
                 else:
                     field_output.extend(ref_output)
             table_output.append(' '.join(field_output))
@@ -267,7 +267,7 @@ class BaseDatabaseCreation(object):
 
         # Get a cursor (even though we don't need one yet). This has
         # the side effect of initializing the test database.
-        cursor = self.connection.cursor()
+        self.connection.cursor()
 
         return test_database_name
 
diff --git a/django/db/models/base.py b/django/db/models/base.py
index 4b3220b514a..b5ce39e3d5a 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -474,7 +474,6 @@ class Model(object):
         ('raw', 'cls', and 'origin').
         """
         using = using or router.db_for_write(self.__class__, instance=self)
-        connection = connections[using]
         assert not (force_insert and force_update)
         if cls is None:
             cls = self.__class__
diff --git a/django/db/models/query.py b/django/db/models/query.py
index 0e1a1b31b41..246b155b0c5 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -9,7 +9,7 @@ from django.db.models.fields import AutoField
 from django.db.models.query_utils import (Q, select_related_descend,
     deferred_class_factory, InvalidQuery)
 from django.db.models.deletion import Collector
-from django.db.models import signals, sql
+from django.db.models import sql
 from django.utils.functional import partition
 
 # Used to control how many objects are worked with at once in some cases (e.g.
diff --git a/django/db/models/sql/compiler.py b/django/db/models/sql/compiler.py
index 9ddcfc63f9c..6bf7de2e210 100644
--- a/django/db/models/sql/compiler.py
+++ b/django/db/models/sql/compiler.py
@@ -1,14 +1,13 @@
 from itertools import izip
 
 from django.core.exceptions import FieldError
-from django.db import connections
 from django.db import transaction
 from django.db.backends.util import truncate_name
+from django.db.models.query_utils import select_related_descend
 from django.db.models.sql.constants import *
 from django.db.models.sql.datastructures import EmptyResultSet
 from django.db.models.sql.expressions import SQLEvaluator
-from django.db.models.sql.query import (get_proxied_model, get_order_dir,
-     select_related_descend, Query)
+from django.db.models.sql.query import get_proxied_model, get_order_dir, Query
 from django.db.utils import DatabaseError
 
 
@@ -875,8 +874,6 @@ class SQLUpdateCompiler(SQLCompiler):
         Creates the SQL for this query. Returns the SQL string and list of
         parameters.
         """
-        from django.db.models.base import Model
-
         self.pre_sql_setup()
         if not self.query.values:
             return '', ()
diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index 101d4ac7a54..61fd2be40b3 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -15,7 +15,7 @@ from django.utils.tree import Node
 from django.db import connections, DEFAULT_DB_ALIAS
 from django.db.models import signals
 from django.db.models.fields import FieldDoesNotExist
-from django.db.models.query_utils import select_related_descend, InvalidQuery
+from django.db.models.query_utils import InvalidQuery
 from django.db.models.sql import aggregates as base_aggregates_module
 from django.db.models.sql.constants import *
 from django.db.models.sql.datastructures import EmptyResultSet, Empty, MultiJoin
@@ -567,7 +567,6 @@ class Query(object):
         field_names, defer = self.deferred_loading
         if not field_names:
             return
-        columns = set()
         orig_opts = self.model._meta
         seen = {}
         if orig_opts.proxy: