CREATE TABLE "image"
(
    "id"   serial NOT NULL PRIMARY KEY,
    "name" text   NOT NULL
);
CREATE TABLE "topic"
(
    "id"       serial  NOT NULL PRIMARY KEY,
    "title"    text    NOT NULL,
    "image_id" integer REFERENCES "image" ("id") NOT NULL
);
CREATE TABLE "user"
(
    "id"   serial NOT NULL PRIMARY KEY,
    "name" text   NOT NULL
);
CREATE TABLE "topic_user"
(
    "id"       serial  NOT NULL PRIMARY KEY,
    "role"     text    NOT NULL,
    "topic_id" integer REFERENCES "topic" ("id") NOT NULL,
    "user_id"  integer REFERENCES "user" ("id") NOT NULL
);
CREATE TABLE "question"
(
    "id"       serial  NOT NULL PRIMARY KEY,
    "text"     text    NOT NULL,
    "topic_id" integer REFERENCES "topic" ("id") NOT NULL 
);

from django.db import models
class Image(models.Model):
    class Meta:
        db_table = 'image'
    name = models.TextField()
class Topic(models.Model):
    class Meta:
        db_table = 'topic'
    title = models.TextField()
    image = models.ForeignKey(Image, on_delete=models.DO_NOTHING)
    users = models.ManyToManyField('User', through='TopicUser')
class Question(models.Model):
    class Meta:
        db_table = 'question'
    text = models.TextField()
    topic = models.ForeignKey(Topic, on_delete=models.DO_NOTHING, related_name='questions')
class TopicUser(models.Model):
    class Meta:
        db_table = 'topic_user'
    topic = models.ForeignKey(Topic, on_delete=models.DO_NOTHING)
    user = models.ForeignKey('User', on_delete=models.DO_NOTHING)
    role = models.TextField(max_length=64)
class User(models.Model):
    class Meta:
        db_table = 'user'
    name = models.TextField()

// генерируем миграцию
python manage.py makemigrations  // появится миграция с номером 0001
// смотрим, какой SQL исполнится в базе при выполнении миграции
python manage.py sqlmigrate topics 0001

'django.db.backends': {
            'level': 'DEBUG',
            'handlers': ['console'],
            'propagate': False,
        },

from django.test import override_settings
@override_settings(DEBUG=True)
def test_i(self):
    <actual_test_code>

SELECT *
FROM question
WHERE topic_id = 1
ORDER BY id DESC
LIMIT 10;

questions = Question.objects.filter(topic_id=self.t1_id).order_by('-id')[:10]

SELECT *
FROM question
WHERE (
  topic_id = 1 AND (
      text ILIKE '%fart%' OR
      NOT (text ILIKE '%dog%')
  )
);

questions = Question.objects.filter(
    Q(topic_id=1),
    Q(text__icontains='fart') | ~Q(text__icontains='dog')
)

SELECT "question"."id", "question"."text", "question"."topic_id"
FROM "question"
WHERE (
    "question"."topic_id" = 1 AND
    (
        UPPER("question"."text"::text) LIKE UPPER('%fart%') OR
        NOT (UPPER("question"."text"::text) LIKE UPPER('%dog%'))
    )
);

q = Question.objects.filter(id=self.q1_id).first()  # dj.3.1
print(q.topic.title)  # dj.3.2

q = Question.objects.select_related('topic').filter(id=self.q1_id).first()  # dj.3.3
print(q.topic.title)  # dj.3.4

SELECT "question"."id",
       "question"."text",
       "question"."topic_id",
       "topic"."id",
       "topic"."title",
       "topic"."image_id"
FROM "question"
         INNER JOIN "topic" ON ("question"."topic_id" = "topic"."id")
WHERE "question"."id" = 1
ORDER BY "question"."id" ASC
LIMIT 1;

for q in Question.objects.all():
    print(q.topic.title)  # dj.4.1
    print(q.topic.image.name)  # dj.4.2

for q in Question.objects.select_related('topic__image').all():  # dj.4.3
    print(q.topic.title)
    print(q.topic.image.name)

SELECT "question"."id",
       "question"."text",
       "question"."topic_id",
       "topic"."id",
       "topic"."title",
       "topic"."image_id",
       "image"."id",
       "image"."name"
FROM "question"
         INNER JOIN "topic" ON ("question"."topic_id" = "topic"."id")
         INNER JOIN "image" ON ("topic"."image_id" = "image"."id");

image = models.ForeignKey(Image, on_delete=models.DO_NOTHING, null=True)

for t in Topic.objects.filter(id__in=(self.t1_id, self.t2_id)):  # dj.5.1
    print([q.text for q in t.questions.all()])  # dj.5.2

for t in Topic.objects.filter(id__in=(self.t1_id, self.t2_id)).prefetch_related('questions'):  # dj.5.3
    print([q.text for q in t.questions.all()])  # dj.5.4

SELECT "topic"."id", "topic"."title", "topic"."image_id"
FROM "topic"
WHERE "topic"."id" IN (1, 2);

SELECT "question"."id", "question"."text", "question"."topic_id"
FROM "question"
WHERE "question"."topic_id" IN (1, 2);

topics_with_filtered_questions = Topic.objects.prefetch_related(Prefetch(
    'questions',
    queryset=Question.objects.filter(text__icontains='fart'),
    to_attr='filtered_questions'
)).all()
for t in topics_with_filtered_questions:
    print(f'{t.title}')
    for q in t.filtered_questions:
        print(f' --- {q.text}')

SELECT "topic"."id", "topic"."title", "topic"."image_id"
FROM "topic";
SELECT "question"."id", "question"."text", "question"."topic_id"
FROM "question"
WHERE (UPPER("question"."text"::text) LIKE UPPER('%fart%')
  AND "question"."topic_id" IN (1, 2));

topic_ids = Question.objects.values('topic_id').annotate(
  qs_count=Count('id'),
).filter(qs_count__gt=10)

topics = Topic.objects.filter(id__in=topic_ids.values('topic_id'))
for t in topics:
    print(f'{t.title}')

SELECT "topic"."id", "topic"."title", "topic"."image_id"
FROM "topic"
WHERE "topic"."id" IN (
    SELECT U0."topic_id"
    FROM "question" U0
    GROUP BY U0."topic_id"
    HAVING COUNT(U0."id") > 10
);

for t in Topic.objects.all():  # dj.9.1
    names = ', '.join(u.name for u in t.users.all())  # dj.9.2
    print(f'Topic[{t.title}]: {names}')

SELECT "topic"."id", "topic"."title", "topic"."image_id" FROM "topic";  -- dj.9.1
SELECT "user"."id", "user"."name"
FROM "user" INNER JOIN "topic_user" ON ("user"."id" = "topic_user"."user_id")
WHERE "topic_user"."topic_id" = 1; -- dj.9.2
SELECT "user"."id", "user"."name"
FROM "user" INNER JOIN "topic_user" ON ("user"."id" = "topic_user"."user_id")
WHERE "topic_user"."topic_id" = 2; -- dj.9.2

for t in Topic.objects.prefetch_related('users'):  # dj.9.3
    names = ', '.join(u.name for u in t.users.all())
    print(f'Topic[{t.title}]: {names}')

SELECT "topic"."id", "topic"."title", "topic"."image_id"
FROM "topic";
SELECT ("topic_user"."topic_id") AS "_prefetch_related_val_topic_id", "user"."id", "user"."name"
FROM "user" INNER JOIN "topic_user" ON ("user"."id" = "topic_user"."user_id")
WHERE "topic_user"."topic_id" IN (1, 2);

u = User.objects.get(id=self.u1_id)  # dj.9.4
for topic_info in u.topicuser_set.all():  # dj.9.5
    print(f'{u.name} is {topic_info.role} in topic "{topic_info.topic.title}"')  # dj.9.6

SELECT "user"."id", "user"."name"
FROM "user"
WHERE "user"."id" = 1;  -- dj.9.4
SELECT "topic_user"."id", "topic_user"."topic_id", "topic_user"."user_id", "topic_user"."role"
FROM "topic_user"
WHERE "topic_user"."user_id" = 1;  -- dj.9.5
SELECT "topic"."id", "topic"."title", "topic"."image_id"
FROM "topic"
WHERE "topic"."id" = 1;  -- dj.9.6
SELECT "topic"."id", "topic"."title", "topic"."image_id"
FROM "topic"
WHERE "topic"."id" = 2;  -- dj.9.6

u = User.objects.prefetch_related('topicuser_set', 'topicuser_set__topic').get(id=self.u1_id)
for topic_info in u.topicuser_set.all():
    print(f'{u.name} is {topic_info.role} in topic "{topic_info.topic.title}"')

SELECT "user"."id", "user"."name"
FROM "user"
WHERE "user"."id" = 1;
SELECT "topic_user"."id", "topic_user"."topic_id", "topic_user"."user_id", "topic_user"."role"
FROM "topic_user"
WHERE "topic_user"."user_id" IN (1);
SELECT "topic"."id", "topic"."title", "topic"."image_id"
FROM "topic"
WHERE "topic"."id" IN (1, 2);

Topic.objects.bulk_create([
    Topic(title=f'topic {i}', image_id=self.i1_id)
    for i in range(10)
], batch_size=2)

INSERT INTO "topic" ("title", "image_id") VALUES
  ('topic 0', 1),
  ('topic 1', 1)
RETURNING "topic"."id";

User.objects.bulk_update(
    [User(id=1, name='new dj 1 name'), User(id=2, name='new dj 2 name')],
    ['name'],
)

UPDATE "user"
SET "name" = (
    CASE
        WHEN ("user"."id" = 1) THEN 'new dj 1 name'
        WHEN ("user"."id" = 2) THEN 'new dj 2 name'
        ELSE NULL END
    )::text
WHERE "user"."id" IN (1, 2);