example_sqlite_.py

import sqlite3
from sqlite3 import Error

def create_connection(path):
    connection = None
    try:
        connection = sqlite3.connect(path)
        print("Connection to SQLite DB successful")
    except Error as e:
        print(f"The error '{e}' occurred")

    return connection

def execute_query(connection, query):
    cursor = connection.cursor()
    try:
        cursor.execute(query)
        connection.commit()
        print("Query executed succcessfully")
    except Error as e:
        print(f"The error '{e}' occurred")

connection = create_connection("D:\\sm_app.sqlite")

create_users_table = """
CREATE TABLE IF NOT EXISTS users(
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    name TEXT NOT NULL,
    age INTEGER,
    gender TEXT,
    nationality TEXT
    );
"""

create_posts_table = """
CREATE TABLE IF NOT EXISTS posts(
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    title TEXT NOT NULL,
    description TEXT NOT NULL,
    user_id INTEGER NOT NULL,
    FOREIGN KEY (user_id) REFERENCES users (id)
    );
"""

create_comments_table = """
CREATE TABLE IF NOT EXISTS comments (
  id INTEGER PRIMARY KEY AUTOINCREMENT, 
  text TEXT NOT NULL, 
  user_id INTEGER NOT NULL, 
  post_id INTEGER NOT NULL, 
  FOREIGN KEY (user_id) REFERENCES users (id) FOREIGN KEY (post_id) REFERENCES posts (id)
);
"""

create_likes_table = """
CREATE TABLE IF NOT EXISTS likes (
  id INTEGER PRIMARY KEY AUTOINCREMENT, 
  user_id INTEGER NOT NULL, 
  post_id integer NOT NULL, 
  FOREIGN KEY (user_id) REFERENCES users (id) FOREIGN KEY (post_id) REFERENCES posts (id)
);
"""
execute_query(connection, create_users_table)
execute_query(connection, create_posts_table)
execute_query(connection, create_comments_table)
execute_query(connection, create_likes_table)

create_users = """
INSERT INTO
  users (name, age, gender, nationality)
VALUES
  ('James', 25, 'male', 'USA'),
  ('Leila', 32, 'female', 'France'),
  ('Brigitte', 35, 'female', 'England'),
  ('Mike', 40, 'male', 'Denmark'),
  ('Elizabeth', 21, 'female', 'Canada');
"""

execute_query(connection, create_users)

create_posts = """
INSERT INTO
  posts (title, description, user_id)
VALUES
  ("Happy", "I am feeling very happy today", 1),
  ("Hot Weather", "The weather is very hot today", 2),
  ("Help", "I need some help with my work", 2),
  ("Great News", "I am getting married", 1),
  ("Interesting Game", "It was a fantastic game of tennis", 5),
  ("Party", "Anyone up for a late-night party today?", 3);
"""
execute_query(connection, create_posts)

create_comments = """
INSERT INTO
  comments (text, user_id, post_id)
VALUES
  ('Count me in', 1, 6),
  ('What sort of help?', 5, 3),
  ('Congrats buddy', 2, 4),
  ('I was rooting for Nadal though', 4, 5),
  ('Help with your thesis?', 2, 3),
  ('Many congratulations', 5, 4);
"""

create_likes = """
INSERT INTO
  likes (user_id, post_id)
VALUES
  (1, 6),
  (2, 3),
  (1, 5),
  (5, 4),
  (2, 4),
  (4, 2),
  (3, 6);
"""

execute_query(connection, create_comments)
execute_query(connection, create_likes)

def execute_read_query(connection, query):
    cursor = connection.cursor()
    result = None
    try:
        cursor.execute(query)
        result = cursor.fetchall()
        return result
    except Error as e:
        print(f"The error '{e}' occurred")

select_users = "SELECT * from users"
users = execute_read_query(connection, select_users)

select_users_posts = """
SELECT
  users.id,
  users.name,
  posts.description
FROM
  posts
  INNER JOIN users ON users.id = posts.user_id
"""

users_posts = execute_read_query(connection, select_users_posts)

#for users_post in users_posts:
#    print(users_post)

select_posts_comments_users = """
SELECT 
    posts.description as post,
    text as comment,
    name
FROM
    posts
    INNER JOIN comments ON posts.id = comments.post_id
    INNER JOIN users ON users.id = comments.user_id
"""

posts_comments_users = execute_read_query(
    connection, select_posts_comments_users
)

for posts_comments_user in posts_comments_users:
    print(posts_comments_user)
select_post_likes = """
SELECT
  description as Post,
  COUNT(likes.id) as Likes
FROM
  likes,
  posts
WHERE
  posts.id = likes.post_id
GROUP BY
  likes.post_id
"""

post_likes = execute_read_query(connection, select_post_likes)

for post_like in post_likes:
    print(post_like)

select_post_description = "SELECT description FROM posts WHERE id = 2"

post_description = execute_read_query(connection, select_post_description)

for description in post_description:
    print(description)

update_post_description = """
UPDATE
  posts
SET
  description = "The weather has become pleasant now"
WHERE
  id = 2
"""
execute_query(connection, update_post_description)

delete_comment = "DELETE FROM comments WHERE id = 5"
execute_query(connection, delete_comment)