01.left-join.md

DROP TABLE IF EXISTS employee;
DROP TABLE IF EXISTS department;
DROP TABLE IF EXISTS location;
DROP TABLE IF EXISTS country;
DROP TABLE IF EXISTS job;
 
CREATE TABLE country (
	country_id   TEXT    NOT NULL,
	country_name TEXT    NOT NULL,
	PRIMARY KEY (country_id)
);
 
CREATE TABLE location (
	location_id    INTEGER NOT NULL,
	street_address TEXT,
	postal_code    TEXT,
	city           TEXT    NOT NULL,
	state_province TEXT,
	country_id     INTEGER NOT NULL,
	PRIMARY KEY (location_id),
	FOREIGN KEY (country_id) REFERENCES country (country_id)
);
 
CREATE TABLE department (
	department_id   INTEGER NOT NULL,
	department_name TEXT    NOT NULL,
	location_id     INTEGER NOT NULL,
	PRIMARY KEY (department_id),
	FOREIGN KEY (location_id) REFERENCES location (location_id)
);
 
CREATE TABLE job (
	job_id     INTEGER NOT NULL,
	job_title  TEXT    NOT NULL,
	min_salary REAL    NOT NULL,
	max_salary REAL    NOT NULL,
	PRIMARY KEY (job_id)
);
 
CREATE TABLE employee (
	employee_id   INTEGER NOT NULL,
	first_name    TEXT,
	last_name     TEXT    NOT NULL,
	email         TEXT    NOT NULL,
	phone_number  TEXT,
	hire_date     TEXT    NOT NULL,
	job_id        INTEGER NOT NULL,
	salary        REAL    NOT NULL,
	department_id INTEGER NOT NULL,
	PRIMARY KEY (employee_id),
	FOREIGN KEY (job_id) REFERENCES job (job_id),
	FOREIGN KEY (department_id) REFERENCES department (department_id)
);
 
-- country
INSERT INTO country(country_id, country_name) VALUES ('AR', 'Argentina');
INSERT INTO country(country_id, country_name) VALUES ('AU', 'Australia');
INSERT INTO country(country_id, country_name) VALUES ('BE', 'Belgium');
INSERT INTO country(country_id, country_name) VALUES ('BR', 'Brazil');
INSERT INTO country(country_id, country_name) VALUES ('CA', 'Canada');
INSERT INTO country(country_id, country_name) VALUES ('CH', 'Switzerland');
INSERT INTO country(country_id, country_name) VALUES ('CN', 'China');
INSERT INTO country(country_id, country_name) VALUES ('DE', 'Germany');
INSERT INTO country(country_id, country_name) VALUES ('DK', 'Denmark');
INSERT INTO country(country_id, country_name) VALUES ('EG', 'Egypt');
INSERT INTO country(country_id, country_name) VALUES ('FR', 'France');
INSERT INTO country(country_id, country_name) VALUES ('HK', 'HongKong');
INSERT INTO country(country_id, country_name) VALUES ('IL', 'Israel');
INSERT INTO country(country_id, country_name) VALUES ('IN', 'India');
INSERT INTO country(country_id, country_name) VALUES ('IT', 'Italy');
INSERT INTO country(country_id, country_name) VALUES ('JP', 'Japan');
INSERT INTO country(country_id, country_name) VALUES ('KW', 'Kuwait');
INSERT INTO country(country_id, country_name) VALUES ('MX', 'Mexico');
INSERT INTO country(country_id, country_name) VALUES ('NG', 'Nigeria');
INSERT INTO country(country_id, country_name) VALUES ('NL', 'Netherlands');
INSERT INTO country(country_id, country_name) VALUES ('SG', 'Singapore');
INSERT INTO country(country_id, country_name) VALUES ('UK', 'United Kingdom');
INSERT INTO country(country_id, country_name) VALUES ('US', 'United States of America');
INSERT INTO country(country_id, country_name) VALUES ('ZM', 'Zambia');
INSERT INTO country(country_id, country_name) VALUES ('ZW', 'Zimbabwe');
 
-- location
INSERT INTO location(location_id, street_address, postal_code, city, state_province, country_id) VALUES (1400, '2014 Jabberwocky Rd', '26192', 'Southlake', 'Texas', 'US');
INSERT INTO location(location_id, street_address, postal_code, city, state_province, country_id) VALUES (1500, '2011 Interiors Blvd', '99236', 'South San Francisco', 'California', 'US');
INSERT INTO location(location_id, street_address, postal_code, city, state_province, country_id) VALUES (1700, '2004 Charade Rd', '98199', 'Seattle', 'Washington', 'US');
INSERT INTO location(location_id, street_address, postal_code, city, state_province, country_id) VALUES (1800, '147 Spadina Ave', 'M5V 2L7', 'Toronto', 'Ontario', 'CA');
INSERT INTO location(location_id, street_address, postal_code, city, state_province, country_id) VALUES (2400, '8204 Arthur St', NULL, 'London', NULL, 'UK');
INSERT INTO location(location_id, street_address, postal_code, city, state_province, country_id) VALUES (2500, 'Magdalen Centre,  The Oxford Science Park', 'OX9 9ZB', 'Oxford', 'Oxford', 'UK');
INSERT INTO location(location_id, street_address, postal_code, city, state_province, country_id) VALUES (2700, 'Schwanthalerstr. 7031', '80925', 'Munich', 'Bavaria', 'DE');
 
-- job
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (1, 'Public Accountant', 4200.00, 9000.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (2, 'Accounting Manager', 8200.00, 16000.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (3, 'Administration Assistant', 3000.00, 6000.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (4, 'President', 20000.00, 40000.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (5, 'Administration Vice President', 15000.00, 30000.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (6, 'Accountant', 4200.00, 9000.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (7, 'Finance Manager', 8200.00, 16000.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (8, 'Human Resources Representative', 4000.00, 9000.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (9, 'Programmer', 4000.00, 10000.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (10, 'Marketing Manager', 9000.00, 15000.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (11, 'Marketing Representative', 4000.00, 9000.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (12, 'Public Relations Representative', 4500.00, 10500.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (13, 'Purchasing Clerk', 2500.00, 5500.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (14, 'Purchasing Manager', 8000.00, 15000.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (15, 'Sales Manager', 10000.00, 20000.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (16, 'Sales Representative', 6000.00, 12000.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (17, 'Shipping Clerk', 2500.00, 5500.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (18, 'Stock Clerk', 2000.00, 5000.00);
INSERT INTO job(job_id, job_title, min_salary, max_salary) VALUES (19, 'Stock Manager', 5500.00, 8500.00);
 
-- department
INSERT INTO department(department_id, department_name, location_id) VALUES (1, 'Administration', 1700);
INSERT INTO department(department_id, department_name, location_id) VALUES (2, 'Marketing', 1800);
INSERT INTO department(department_id, department_name, location_id) VALUES (3, 'Purchasing', 1700);
INSERT INTO department(department_id, department_name, location_id) VALUES (4, 'Human Resources', 2400);
INSERT INTO department(department_id, department_name, location_id) VALUES (5, 'Shipping', 1500);
INSERT INTO department(department_id, department_name, location_id) VALUES (6, 'IT', 1400);
INSERT INTO department(department_id, department_name, location_id) VALUES (7, 'Public Relations', 2700);
INSERT INTO department(department_id, department_name, location_id) VALUES (8, 'Sales', 2500);
INSERT INTO department(department_id, department_name, location_id) VALUES (9, 'Executive', 1700);
INSERT INTO department(department_id, department_name, location_id) VALUES (10, 'Finance', 1700);
INSERT INTO department(department_id, department_name, location_id) VALUES (11, 'Accounting', 1700);
 
-- employee
INSERT INTO employee(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, department_id) VALUES (100, 'Steven', 'King', '[email protected]', '515.123.4567', '1987-06-17', 4, 24000.00, 9);
INSERT INTO employee(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, department_id) VALUES (101, 'Neena', 'Kochhar', '[email protected]', '515.123.4568', '1989-09-21', 5, 17000.00, 9);
INSERT INTO employee(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, department_id) VALUES (102, 'Lex', 'De Haan', 'lex.de [email protected]', '515.123.4569', '1993-01-13', 5, 17000.00, 9);
INSERT INTO employee(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, department_id) VALUES (103, 'Alexander', 'Hunold', '[email protected]', '590.423.4567', '1990-01-03', 9, 9000.00, 6);
INSERT INTO employee(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, department_id) VALUES (104, 'Bruce', 'Ernst', '[email protected]', '590.423.4568', '1991-05-21', 9, 6000.00, 6);
INSERT INTO employee(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, department_id) VALUES (105, 'David', 'Austin', '[email protected]', '590.423.4569', '1997-06-25', 9, 4800.00, 6);
INSERT INTO employee(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, department_id) VALUES (106, 'Valli', 'Pataballa', '[email protected]', '590.423.4560', '1998-02-05', 9, 4800.00, 6);
INSERT INTO employee(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, department_id) VALUES (107, 'Diana', 'Lorentz', '[email protected]', '590.423.5567', '1999-02-07', 9, 4200.00, 6);
INSERT INTO employee(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, department_id) VALUES (108, 'Nancy', 'Greenberg', '[email protected]', '515.124.4569', '1994-08-17', 7, 12000.00, 10);
INSERT INTO employee(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, department_id) VALUES (109, 'Daniel', 'Faviet', '[email protected]', '515.124.4169', '1994-08-16', 6, 9000.00, 10);
INSERT INTO employee(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, department_id) VALUES (110, 'John', 'Chen', '[email protected]', '515.124.4269', '1997-09-28', 6, 8200.00, 10);
INSERT INTO employee(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, department_id) VALUES (111, 'Ismael', 'Sciarra', '[email protected]', '515.124.4369', '1997-09-30', 6, 7700.00, 10);
INSERT INTO employee(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, department_id) VALUES (112, 'Jose Manuel', 'Urman', 'jose [email protected]', '515.124.4469', '1998-03-07', 6, 7800.00, 10);
INSERT INTO employee(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, department_id) VALUES (113, 'Luis', 'Popp', '[email protected]', '515.124.4567', '1999-12-07', 6, 6900.00, 10);
INSERT INTO employee(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, department_id) VALUES (114, 'Den', 'Raphaely', '[email protected]', '515.127.4561', '1994-12-07', 14, 11000.00, 3);

1. Create a LEFT JOIN of tables:

• department

• location

  using the location_id column. Display all columns in the result.

---

2. Create a LEFT JOIN of tables:

• department
• location

using the location_id column. Display the following columns in the output table:

• department_id
• department_name
• street_address
• city

---

3. Create a LEFT JOIN (in the given order) of tables:

• department
• location
• country

using the location_id and country_id columns respectively. Display all columns in the result table.

---

4. Create a LEFT JOIN of tables:

• department
• location
• country

using the location_id and country_id columns respectively. In the result table, display the columns:

• department_id
• department_name
• street_address
• city
• country_name

---

5. Create a LEFT JOIN of tables:

• employee
• job

using the job_id column. Display all columns in the result table.

---

6. Create a LEFT JOIN of tables:

• employee
• job

using the job_id column. In the output table, display the following columns:

• employee_id
• email
• salary
• job_title

---

7. The following query is given:

SELECT
  t1.employee_id,
  t1.email,
  t1.salary,
  t2.job_title
FROM
  employee AS t1
LEFT JOIN job AS t2 ON t1.job_id = t2.job_id;

Modify the above query to extract the rows with salary greater than 8000. Sort the result in descending order by salary.

---

8. Create a LEFT JOIN of tables:

• employee
• job
• department

using the job_id and department_id columns respectively. In the output table, display the following columns:

• employee_id
• email
• salary
• job_title
• department_name

---

9. The following query is given:

SELECT
  t1.employee_id,
  t1.email,
  t1.salary,
  t2.job_title,
  t3.department_name
FROM
  employee AS t1
LEFT JOIN job AS t2 ON t1.job_id = t2.job_id
LEFT JOIN department AS t3 ON t1.department_id = t3.department_id;

Modify the above query. Group the data at the department_name level and calculate the number of employees for each department. Assign the alias number_of_employees to the result. Sort the output table by decreasing number_of_employees. The output table should contain two columns:

• department_name
• number_of_employees

---

10. The following query is given:

SELECT
  t1.employee_id,
  t1.email,
  t1.salary,
  t2.job_title,
  t3.department_name
FROM
  employee AS t1
LEFT JOIN job AS t2 ON t1.job_id = t2.job_id
LEFT JOIN department AS t3 ON t1.department_id = t3.department_id;

Modify the above query. Group the data on the job_title level and calculate the number of employees for each position. Assign the alias number_of_employees to the result. Also, find the average salary for the position and assign the alias avg_salary. Sort the result by descending avg_salary.

The output table should contain three columns:

• job_title
• number_of_employees
• avg_salary

---

11. Create a LEFT JOIN of tables:

• location
• country

using the country_id column. Display all columns in the output table.

---

12. Create a LEFT JOIN of tables:

• location
• country

using the country_id column.

In the output table, display the following columns:

• location_id
• street_address
• city
• country_name

Sort the output table in ascending order by country_name.

02.inner-join.md

DROP TABLE IF EXISTS product;
DROP TABLE IF EXISTS category;
DROP TABLE IF EXISTS brand;
 
CREATE TABLE category (
	category_id   INTEGER NOT NULL,
	category_name TEXT    NOT NULL,
	PRIMARY KEY (category_id)
);
 
CREATE TABLE brand (
	brand_id   INTEGER NOT NULL,
	brand_name TEXT    NOT NULL,
	PRIMARY KEY (brand_id)
);
 
CREATE TABLE product (
	product_id   INTEGER NOT NULL,
	product_name TEXT    NOT NULL,
	brand_id     INTEGER NOT NULL,
	category_id  INTEGER,
	model_year   INTEGER NOT NULL,
	list_price   REAL    NOT NULL,
	PRIMARY KEY (product_id),
	FOREIGN KEY (category_id) REFERENCES category (category_id),
	FOREIGN KEY (brand_id) REFERENCES brand (brand_id)
);
 
-- category
INSERT INTO category (category_id, category_name) VALUES (1, 'Children Bicycles');
INSERT INTO category (category_id, category_name) VALUES (2, 'Comfort Bicycles');
INSERT INTO category (category_id, category_name) VALUES (3, 'Cruisers Bicycles');
INSERT INTO category (category_id, category_name) VALUES (4, 'Cyclocross Bicycles');
INSERT INTO category (category_id, category_name) VALUES (5, 'Electric Bikes');
INSERT INTO category (category_id, category_name) VALUES (6, 'Mountain Bikes');
INSERT INTO category (category_id, category_name) VALUES (7, 'Road Bikes');
 
-- brand 
INSERT INTO brand (brand_id, brand_name) VALUES (1, 'Electra');
INSERT INTO brand (brand_id, brand_name) VALUES (2, 'Haro');
INSERT INTO brand (brand_id, brand_name) VALUES (3, 'Heller');
INSERT INTO brand (brand_id, brand_name) VALUES (4, 'Pure Cycles');
INSERT INTO brand (brand_id, brand_name) VALUES (5, 'Ritchey');
INSERT INTO brand (brand_id, brand_name) VALUES (6, 'Strider');
INSERT INTO brand (brand_id, brand_name) VALUES (7, 'Sun Bicycles');
INSERT INTO brand (brand_id, brand_name) VALUES (8, 'Surly');
INSERT INTO brand (brand_id, brand_name) VALUES (9, 'Trek');
 
-- product
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (1, 'Trek 820 - 2021', 9, 6, 2021, 379.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (2, 'Ritchey Timberwolf Frameset - 2021', 5, 6, 2021, 749.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (3, 'Surly Wednesday Frameset - 2021', 8, 6, 2021, 999.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (4, 'Trek Fuel EX 8 29 - 2021', 9, 6, 2021, 2899.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (5, 'Heller Shagamaw Frame - 2021', 3, NULL, 2021, 1320.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (6, 'Surly Ice Cream Truck Frameset - 2021', 8, 6, 2021, 469.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (7, 'Trek Slash 8 27.5 - 2021', 9, 6, 2021, 3999.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (8, 'Trek Remedy 29 Carbon Frameset - 2021', 9, 6, 2021, 1799.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (9, 'Trek Conduit+ - 2021', 9, 5, 2021, 2999.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (10, 'Surly Straggler - 2021', 8, 4, 2021, 1549);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (11, 'Surly Straggler 650b - 2021', 8, 4, 2021, 1680.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (12, 'Electra Townie Original 21D - 2021', 1, NULL, 2021, 549.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (13, 'Electra Cruiser 1 (24-Inch) - 2021', 1, NULL, 2021, 269.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (14, 'Electra Girl''s Hawaii 1 (16-inch) - 2020/2021', 1, 3, 2021, 269.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (15, 'Electra Moto 1 - 2021', 1, 3, 2021, 529.99);

1. Create an INNER JOIN of tables:

• product
• category

Use the category_id column to join the tables. Notice that the category_id column in the product table contains NULL values.

---

2. Create an INNER JOIN of tables:

• product
• category

Use the category_id column to join the tables. Display the following columns in the output table:

• product_id
• product_name
• list_price
• category_name

---

3. The following query is given:

SELECT
  t1.product_id,
  t1.product_name,
  t1.list_price,
  t2.category_name
FROM
  product AS t1
INNER JOIN category AS t2 ON t1.category_id = t2.category_id;

Modify the given query to group the data on the category_name level. Calculate the number of products for each category and assign an alias number_of_products. The output table should contain two columns:

• category_name
• number_of_products

Sort output table in descending order by number_of_products.

---

DROP TABLE IF EXISTS order_01_2021;
DROP TABLE IF EXISTS order_02_2021;
DROP TABLE IF EXISTS product;
DROP TABLE IF EXISTS category;
DROP TABLE IF EXISTS brand;
 
CREATE TABLE category (
	category_id   INTEGER NOT NULL,
	category_name TEXT    NOT NULL,
	PRIMARY KEY (category_id)
);
 
CREATE TABLE brand (
	brand_id   INTEGER NOT NULL,
	brand_name TEXT    NOT NULL,
	PRIMARY KEY (brand_id)
);
 
CREATE TABLE product (
	product_id   INTEGER NOT NULL,
	product_name TEXT    NOT NULL,
	brand_id     INTEGER NOT NULL,
	category_id  INTEGER,
	model_year   INTEGER NOT NULL,
	list_price   REAL    NOT NULL,
	PRIMARY KEY (product_id),
	FOREIGN KEY (category_id) REFERENCES category (category_id),
	FOREIGN KEY (brand_id) REFERENCES brand (brand_id)
);
 
CREATE TABLE order_01_2021 (
	order_id   INTEGER NOT NULL,
	product_id INTEGER NOT NULL,
	quantity   INTEGER NOT NULL,
	PRIMARY KEY (order_id),
	FOREIGN KEY (product_id) REFERENCES product (product_id)
);
 
CREATE TABLE order_02_2021 (
	order_id   INTEGER NOT NULL,
	product_id INTEGER NOT NULL,
	quantity   INTEGER NOT NULL,
	PRIMARY KEY (order_id),
	FOREIGN KEY (product_id) REFERENCES product (product_id)
);
 
-- category
INSERT INTO category (category_id, category_name) VALUES (1, 'Children Bicycles');
INSERT INTO category (category_id, category_name) VALUES (2, 'Comfort Bicycles');
INSERT INTO category (category_id, category_name) VALUES (3, 'Cruisers Bicycles');
INSERT INTO category (category_id, category_name) VALUES (4, 'Cyclocross Bicycles');
INSERT INTO category (category_id, category_name) VALUES (5, 'Electric Bikes');
INSERT INTO category (category_id, category_name) VALUES (6, 'Mountain Bikes');
INSERT INTO category (category_id, category_name) VALUES (7, 'Road Bikes');
 
-- brand 
INSERT INTO brand (brand_id, brand_name) VALUES (1, 'Electra');
INSERT INTO brand (brand_id, brand_name) VALUES (2, 'Haro');
INSERT INTO brand (brand_id, brand_name) VALUES (3, 'Heller');
INSERT INTO brand (brand_id, brand_name) VALUES (4, 'Pure Cycles');
INSERT INTO brand (brand_id, brand_name) VALUES (5, 'Ritchey');
INSERT INTO brand (brand_id, brand_name) VALUES (6, 'Strider');
INSERT INTO brand (brand_id, brand_name) VALUES (7, 'Sun Bicycles');
INSERT INTO brand (brand_id, brand_name) VALUES (8, 'Surly');
INSERT INTO brand (brand_id, brand_name) VALUES (9, 'Trek');
 
-- product
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (1, 'Trek 820 - 2021', 9, 6, 2021, 379.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (2, 'Ritchey Timberwolf Frameset - 2021', 5, 6, 2021, 749.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (3, 'Surly Wednesday Frameset - 2021', 8, 6, 2021, 999.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (4, 'Trek Fuel EX 8 29 - 2021', 9, 6, 2021, 2899.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (5, 'Heller Shagamaw Frame - 2021', 3, 6, 2021, 1320.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (6, 'Surly Ice Cream Truck Frameset - 2021', 8, 6, 2021, 469.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (7, 'Trek Slash 8 27.5 - 2021', 9, 6, 2021, 3999.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (8, 'Trek Remedy 29 Carbon Frameset - 2021', 9, 6, 2021, 1799.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (9, 'Trek Conduit+ - 2021', 9, 5, 2021, 2999.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (10, 'Surly Straggler - 2021', 8, 4, 2021, 1549);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (11, 'Surly Straggler 650b - 2021', 8, 4, 2021, 1680.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (12, 'Electra Townie Original 21D - 2021', 1, 3, 2021, 549.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (13, 'Electra Cruiser 1 (24-Inch) - 2021', 1, 3, 2021, 269.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (14, 'Electra Girl''s Hawaii 1 (16-inch) - 2020/2021', 1, 3, 2021, 269.99);
INSERT INTO product (product_id, product_name, brand_id, category_id, model_year, list_price) VALUES (15, 'Electra Moto 1 - 2021', 1, 3, 2021, 529.99);
 
-- order_01_2021
INSERT INTO order_01_2021 (order_id, product_id, quantity) VALUES (1, 3, 1);
INSERT INTO order_01_2021 (order_id, product_id, quantity) VALUES (2, 12, 1);
INSERT INTO order_01_2021 (order_id, product_id, quantity) VALUES (3, 1, 2);
INSERT INTO order_01_2021 (order_id, product_id, quantity) VALUES (4, 4, 1);
INSERT INTO order_01_2021 (order_id, product_id, quantity) VALUES (5, 8, 3);
INSERT INTO order_01_2021 (order_id, product_id, quantity) VALUES (6, 9, 1);
INSERT INTO order_01_2021 (order_id, product_id, quantity) VALUES (7, 5, 1);
 
-- order_02_2021
INSERT INTO order_02_2021 (order_id, product_id, quantity) VALUES (1, 6, 1);
INSERT INTO order_02_2021 (order_id, product_id, quantity) VALUES (2, 10, 1);
INSERT INTO order_02_2021 (order_id, product_id, quantity) VALUES (3, 1, 2);
INSERT INTO order_02_2021 (order_id, product_id, quantity) VALUES (4, 2, 1);
INSERT INTO order_02_2021 (order_id, product_id, quantity) VALUES (5, 7, 3);
INSERT INTO order_02_2021 (order_id, product_id, quantity) VALUES (6, 8, 1);
INSERT INTO order_02_2021 (order_id, product_id, quantity) VALUES (7, 5, 2);
INSERT INTO order_02_2021 (order_id, product_id, quantity) VALUES (9, 11, 1);
INSERT INTO order_02_2021 (order_id, product_id, quantity) VALUES (10, 9, 1);

4. Create an INNER JOIN of tables:

• order_01_2021
• product

using the product_id column. In the output table, display the following columns:

• quantity
• list_price

Also add a third column that calculates the total sales for the record (quantity * list_price) and assign the alias total_price.

---

5. The following query is given:

SELECT
  t1.quantity,
  t2.list_price,
  t1.quantity * t2.list_price AS total_price
FROM
  order_01_2021 AS t1
INNER JOIN product AS t2 ON t1.product_id = t2.product_id;

Modify the above query to find the total sales for January and assign the alias total_sales.

left join:
2

SELECT department_id, department_name, street_address, city 
FROM department as d
LEFT JOIN location as l
USING (location_id);

left join

3

SELECT * 
FROM department 
LEFT JOIN location 
	USING(location_id) 
LEFT JOIN country 
	USING (country_id)

4

SELECT 
	department_id,
	department_name,
	street_address,
	city,
	country_name
FROM department
LEFT JOIN location
    USIng (location_id)
LEFT JOIN country
	USING (country_id)

5

SELECT * FROM employee
LEFT JOIN job
USING (job_id)

SELECT
  t1.employee_id,
  t1.email,
  t1.salary,
  t2.job_title
FROM
  employee AS t1
LEFT JOIN job AS t2
	USING(job_id)
WHERE salary > 8000
ORDER BY salary DESC;

9

SELECT 
	department_name,
	count(employee_id) as number_of_employees 
FROM employee
LEFT JOIN job 
	USING (job_id)
LEFT JOIN department 
	USING (department_id)
GROUP BY 1
ORDER By 2 DESC;

SELECT 
	job_title,
	count(employee_id) AS number_of_employees, 
    AVG(salary) as avg_salary
FROM employee
LEFT JOIN job USING (job_id)
LEFT JOIN department USING (department_id)
GROUP BY 1
ORDER By 3 DESC