Solved LAB | SQL Basic Queries

HOW TO SQL V2.sql

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+-- ===============================================================================================================
+-- HOW TO --------------------------------------------------------------------------------------------------------
+-- How to display all availables tables in a database
+USE database_name;
+SHOW TABLES;
+-- ---------------------------------------------------------------------------------------------------------------
+-- How to display all availables data in a table
+USE database_name;
+SELECT * FROM table_name;
+-- ---------------------------------------------------------------------------------------------------------------
+-- How to 
+DESCRIBE table_name;
+SHOW COLUMNS FROM table_name;
+-- ===============================================================================================================
+-- QUESTIONS!
+
+-- ===============================================================================================================

HOW TO SQL.sql

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+-- ===============================================================================================================
+-- HOW TO --------------------------------------------------------------------------------------------------------
+-- How to drop a table from a database
+DROP TABLE `table_name`;
+-- ---------------------------------------------------------------------------------------------------------------
+-- How to alter a table and drop a foreign key
+ALTER TABLE `table_name`
+DROP FOREIGN KEY `foreign_key_name`;
+-- ---------------------------------------------------------------------------------------------------------------
+
+-- How to add constraints (Foreign keys to a table)
+-- only add to the one that has a many or depends on it
+-- Alter the table with constraints (relationships)
+ALTER TABLE `table_name`
+ADD CONSTRAINT `constraint_name` FOREIGN KEY (`foreign key name`) REFERENCES source_table(`foreign key name`),
+ADD CONSTRAINT `constraint_name` FOREIGN KEY (`foreign key name`) REFERENCES source_table(`foreign key name`),
+ADD CONSTRAINT `constraint_name` FOREIGN KEY (`foreign key name`) REFERENCES source_table(`foreign key name`);
+-- ---------------------------------------------------------------------------------------------------------------
+-- How to seed data into a table
+	-- download the table you want to seed from as a .csv file
+	-- import it into your database
+	-- take data columns from it to the column of the table u wanna seed it in
+	-- INSERT DATA INTO TABLE INVOICES  from different tables 
+INSERT INTO TABLE ('column_1', 'column_2', 'column_3')
+SELECT 'column_1' FROM 'source_1,
+SELECT 'column_2' FROM 'source_2,
+SELECT 'column_3' FROM 'source_3,
+GROUP BY
+	'column_1', 
+    'column_2', 
+    'column_3';
+-- ===============================================================================================================
+-- QUESTIONS!
+-- When to use VARCHAR or CHAR?
+-- What's the difference between CHAR, VARCHAR, TEXT?
+-- Storage engine must support FK? What does it mean exactly?
+SHOW TABLE STATUS WHERE Name = 'table_name';
+-- ===============================================================================================================

challenge solved.sql

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+-- ===============================================================================================================
+-- 1. Display all available tables in the Sakila database.
+USE sakila;
+SHOW TABLES;
+-- ===============================================================================================================
+-- 2. Retrieve all the data from the tables `actor`, `film` and `customer`.
+SELECT * FROM actor;
+SELECT * FROM film; -- original_language_id is null?
+SELECT * FROM customer;
+-- ===============================================================================================================
+-- 3. Retrieve the following columns from their respective tables:
+--
+-- 3.1 Titles of all films from the `film` table
+SELECT title FROM film;
+--
+-- 3.2 List of languages used in films, with the column aliased as `language` from the `language` table
+SELECT language_id AS language FROM film;
+--
+-- 3.3 List of first names of all employees from the `staff` table
+SELECT first_name AS first_name FROM staff;
+
+-- ===============================================================================================================
+-- 4. Retrieve unique release years.
+SELECT DISTINCT release_year FROM film; -- same as python df[column].unique()
+-- ===============================================================================================================
+-- 5. Counting records for database insights:  COUNT
+--
+-- 5.1 Determine the number of stores that the company has.
+SELECT * FROM store;
+SELECT COUNT(store_id) AS nbr_stores FROM store;
+--
+-- 5.2 Determine the number of employees that the company has.
+SELECT * FROM staff;
+SELECT COUNT(staff_id) AS nbr_employees FROM staff;
+--
+-- 5.3 Determine how many films are available for rent and how many have been rented.
+SELECT * FROM film;
+DESCRIBE film;
+
+-- struggled a bit with this one
+--
+-- Number of all films
+SELECT COUNT(*) AS nbr_films_all FROM film;
+SELECT * FROM film;
+--
+-- Number of films available for rent
+SELECT * FROM inventory;
+SELECT DISTINCT film_id FROM inventory;
+SELECT COUNT(DISTINCT film_id) AS nbr_films_available_for_rent FROM inventory;
+--
+-- Number of films that have been rented
+SELECT * FROM rental;
+SELECT COUNT(DISTINCT rental_id) AS number_of_films_rented
+FROM rental;
+
+--
+-- 5.4 Determine the number of distinct last names of the actors in the database.
+SELECT DISTINCT last_name AS actors_last_name FROM actor;
+SELECT COUNT(DISTINCT last_name) AS nbr_actors_last_name FROM actor; -- i mixed up the distinct before count
+-- ===============================================================================================================
+-- 6. Retrieve the 10 longest films.
+-- method 1 : ORDER BY / DESC LIMIT 10
+SELECT * FROM film ORDER BY length DESC LIMIT 10;
+-- method 2 : WHERE column = (SELECT MAX(column)FROM table_name)
+SELECT * FROM film WHERE length = (SELECT MAX(length) FROM film);
+-- ===============================================================================================================
+-- 7.  Use filtering techniques in order to:
+--
+-- 7.1 Retrieve all actors with the first name "SCARLETT".
+SELECT * FROM actor;
+SELECT * FROM actor WHERE first_name = 'SCARLETT';
+--
+-- 7.2 Retrieve all movies that have ARMAGEDDON in their title and have a duration longer than 100 minutes. 
+-- **Hint: use `LIKE` operator. [More information here.](https://www.w3schools.com/sql/sql_like.asp)**
+SELECT * FROM film WHERE title LIKE 'ARMAGEDDON'; -- false gotta use regex
+SELECT * FROM film WHERE title LIKE '%ARMAGEDDON%';
+SELECT * FROM film WHERE title LIKE '%ARMAGEDDON%' AND length > 100;
+--
+-- 7.3 Determine the number of films that include Behind the Scenes content
+SELECT * FROM film;
+SELECT * FROM film WHERE special_features LIKE '%Behind the Scenes%';
+SELECT COUNT(*) FROM film WHERE special_features LIKE '%Behind the Scenes%';
+SELECT COUNT(*) AS films_behind_the_scenes FROM film WHERE special_features LIKE '%Behind the Scenes%';
+-- ===============================================================================================================