Denis p/week2

week-1/mandatory/2-classes-db/task.md

@@ -16,22 +16,122 @@ When you have finished all of the questions - open a pull request with your answ
 ## Task
 
 1. Create a new database called `cyf_classes` (hint: use `createdb` in the terminal)
+
+//ANSWER:
+ createdb cyf_classes
+
 2. Create a new table `mentors`, for each mentor we want to save their name, how many years they lived in Glasgow, their address and their favourite programming language.
+
+//ANSWER:
+
+CREATE TABLE mentors(
+    id SERIAL PRIMARY KEY,
+    name VARCHAR(20),
+    years_in_glasgow VARCHAR(5),
+    address VARCHAR(30),
+    fav_programming_lang VARCHAR(20)
+);
+
 3. Insert 5 mentors in the `mentors` table (you can make up the data, it doesn't need to be accurate ;-)).
+
+//ANSWER:
+
+INSERT INTO mentors(id, name, years_in_glasgow, address, fav_programming_lang) VALUES ('1', 'Mentor1', '3', '10 High Street', 'JavaScript');
+INSERT INTO mentors(id, name, years_in_glasgow, address, fav_programming_lang) VALUES ('2', 'Mentor2', '6', '20 High Street', 'C++');
+INSERT INTO mentors(id, name, years_in_glasgow, address, fav_programming_lang) VALUES ('3', 'Mentor3', '2', '40 High Street', 'C#');
+INSERT INTO mentors(id, name, years_in_glasgow, address, fav_programming_lang) VALUES ('4', 'Mentor4', '8', '82 High Street', 'Python');
+INSERT INTO mentors(id, name, years_in_glasgow, address, fav_programming_lang) VALUES ('5', 'Mentor5', '1', '91 High Street', 'C');
+
 4. Create a new table `students`, for each student we want to save their name, address and if they have graduated from Code Your Future.
+
+//ANSWER:
+
+CREATE TABLE students(
+    id SERIAL PRIMARY KEY,
+    name VARCHAR(20),
+    address VARCHAR(30),
+    cyf_graduated VARCHAR(20)
+);
+
 5. Insert 10 students in the `students` table.
+
+//ANSWER:
+
+INSERT INTO students(id, name, address, cyf_graduated) VALUES ('1', 'Student1','10 Bake Street', 'yes');
+INSERT INTO students(id, name, address, cyf_graduated) VALUES ('2', 'Student2','20 Bake Street', 'no');
+INSERT INTO students(id, name, address, cyf_graduated) VALUES ('3', 'Student3','40 Bake Street', 'no');
+INSERT INTO students(id, name, address, cyf_graduated) VALUES ('4', 'Student4','82 Bake Street', 'yes');
+INSERT INTO students(id, name, address, cyf_graduated) VALUES ('5', 'Student5','91 Bake Street', 'no');
+INSERT INTO students(id, name, address, cyf_graduated) VALUES ('6', 'Student6','10 Bake Street', 'yes');
+INSERT INTO students(id, name, address, cyf_graduated) VALUES ('7', 'Student7','20 Bake Street', 'no');
+INSERT INTO students(id, name, address, cyf_graduated) VALUES ('8', 'Student8','40 Bake Street', 'no');
+INSERT INTO students(id, name, address, cyf_graduated) VALUES ('9', 'Student9','82 Bake Street', 'yes');
+INSERT INTO students(id, name, address, cyf_graduated) VALUES ('10', 'Student10','91 Bake Street', 'yes');
 6. Verify that the data you created for mentors and students are correctly stored in their respective tables (hint: use a `select` SQL statement).
+
+//ANSWER:
+
+SELECT * FROM mentors;
+SELECT * FROM students;
+
 7. Create a new `classes` table to record the following information:
 
    - A class has a leading mentor
    - A class has a topic (such as Javascript, NodeJS)
    - A class is taught at a specific date and at a specific location
 
+//ANSWER:
+
+CREATE TABLE classes(
+    id SERIAL PRIMARY KEY,
+    mentor VARCHAR(20),
+    topic VARCHAR(20),
+    date VARCHAR(15),
+    location VARCHAR(20)
+);
+
 8. Insert a few classes in the `classes` table
+
+//ANSWER:
+
+INSERT INTO classes(id, mentor, topic, date, location) VALUES ('1', 'Mentor1','JavaScript', '2020-01-02', 'Birmingham');
+INSERT INTO classes(id, mentor, topic, date, location) VALUES ('2', 'Mentor2','HTML', '2020-01-09', 'London');
+INSERT INTO classes(id, mentor, topic, date, location) VALUES ('3', 'Mentor3','CSS', '2020-01-16', 'Manchester');
+INSERT INTO classes(id, mentor, topic, date, location) VALUES ('4', 'Mentor4','React', '2020-01-23', 'Glasgow');
+INSERT INTO classes(id, mentor, topic, date, location) VALUES ('5', 'Mentor5','Node', '2020-02-01', 'London');
+
+
 9. We now want to store who among the students attends a specific class. How would you store that? Come up with a solution and insert some data if you model this as a new table.
+
+//ANSWER:
+
+CREATE TABLE classes_attended (
+  id               SERIAL PRIMARY KEY,
+  class      INT REFERENCES classes(id),
+  student     INT REFERENCES students(id)
+);
+
+
+INSERT INTO classes_attended (id, class, student) VALUES (1, 1, 1);
+INSERT INTO classes_attended (id, class, student) VALUES (2, 1, 2);
+INSERT INTO classes_attended (id, class, student) VALUES (3, 2, 3);
+INSERT INTO classes_attended (id, class, student) VALUES (4, 4, 1);
+INSERT INTO classes_attended (id, class, student) VALUES (5, 3, 1);
+INSERT INTO classes_attended (id, class, student) VALUES (6, 5, 4);
+
 10. Answer the following questions using a `select` SQL statement:
     - Retrieve all the mentors who lived more than 5 years in Glasgow
+        //ANSWER:
+        SELECT * FROM mentors WHERE years_in_glasgow > '5';
     - Retrieve all the mentors whose favourite language is Javascript
+        //ANSWER:
+        SELECT * FROM mentors WHERE fav_programming_lang = 'JavaScript';
     - Retrieve all the students who are CYF graduates
+        //ANSWER:
+        SELECT * FROM students WHERE cyf_graduated = 'yes';
     - Retrieve all the classes taught before June this year
+        //ANSWER:
+        SELECT * FROM classes WHERE date < '2020-06-01';
     - Retrieve all the students (retrieving student ids only is fine) who attended the Javascript class (or any other class that you have in the `classes` table).
+        //ANSWER:
+        SELECT student FROM classes_attended WHERE class = '1';

week-2/mandatory/2-ecommerce-db/task.md

@@ -9,6 +9,18 @@ Below you will find a set of tasks for you to complete to set up a databases of
 To submit this homework write the correct commands for each question here:
 
 ```sql
+1. SELECT name, address FROM customers WHERE country = 'United States';
+2. SELECT * FROM customers ORDER BY name;
+3. SELECT * FROM products WHERE unit_price > 100;
+4. SELECT * FROM products WHERE product_name LIKE '%socks%';
+5. SELECT * FROM products ORDER BY unit_price DESC LIMIT 5;
+6. SELECT product_name, unit_price, supplier_name FROM products INNER JOIN suppliers ON suppliers.id = products.supplier_id;
+7. SELECT product_name, supplier_name FROM products INNER JOIN suppliers ON suppliers.country = 'United Kingdom';
+8. SELECT * FROM orders WHERE customer_id = 1;
+9. SELECT * FROM orders INNER JOIN customers ON customers.id = orders.customer_id WHERE customers.name = 'Hope Crosby';
+10. SELECT product_name, unit_price, quantity FROM order_items INNER JOIN products ON products.id = order_items.product_id INNER  JOIn orders ON orders.id = order_items.order_id WHERE orders.order_reference = 'ORD006';
+11. SELECT customers.name, orders.order_reference, orders.order_date, products.product_name, suppliers.supplier_name ,order_items.quantity FROM customers INNER JOIN orders ON orders.customer_id=customers.id INNER JOIN order_items ON orders.id= order_items.order_id INNER JOIN products ON order_items.product_id = products.id INNER JOIN suppliers ON suppliers.id= products.supplier_id;
+12 .SELECT DISTINCT customers.name FROM customers, products, suppliers, orders ,order_items WHERE customers.id = orders.customer_id AND orders.id = order_items.order_id AND order_items.product_id = products.id AND suppliers.id = products.supplier_id AND suppliers.country='China';
 
 
 ```