solving week8 homework

.gitignore

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+database.ini

IT_company_explanation.txt

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+-In the table 'employees', each employee has an id, name and responsibility id,which is a foreign key 
+referring to the same column in table 'responsibility'.
+Each employee has also a team id , which is also a foreign key references the team id in table teams
+
+- In the table 'teams' , each team has an id , a product , a customer. 
+Last two reference the same columns in tables  products and customers respectively.

config.py

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+#!/usr/bin/python
+from configparser import ConfigParser
+
+def config(filename='database.ini', section='postgresql'):
+    # create a parser
+    parser = ConfigParser()
+    # read config file
+    parser.read(filename)
+
+    # get section, default to postgresql
+    db = {}
+    if parser.has_section(section):
+        params = parser.items(section)
+        for param in params:
+            db[param[0]] = param[1]
+    else:
+        raise Exception('Section {0} not found in the {1} file'.format(section, filename))
+
+    return db
+
+# print (config())    

conncet.py

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+#!/usr/bin/python
+import psycopg2
+from config import config
+
+def connect(sql):
+    """ Connect to the PostgreSQL database server and run an sql command and print the results"""
+    conn = None
+    try:
+        # read connection parameters
+        params = config()
+        # connect to the PostgreSQL server
+        print('Connecting to the PostgreSQL database...')
+        conn = psycopg2.connect(**params)
+		        # create a cursor
+        cur = conn.cursor()
+        	# execute a statement
+
+        cur.execute(sql)
+
+        # return the command results :
+        result = cur.fetchall()
+        for r in result:
+            print (r)
+        # print(result)
+
+	# close the communication with the PostgreSQL
+        cur.close()
+    except (Exception, psycopg2.DatabaseError) as error:
+        print(error)
+    finally:
+        if conn is not None:
+            conn.close()
+            print('Database connection closed.')
+
+if __name__ == '__main__':
+   connect('select * from actor')
+   connect('select * from category limit 1')
+   connect('select * from address limit 50')
+

exercise5.py

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+#!/usr/bin/python
+import psycopg2
+# from config import config
+
+def connect(sql):
+    """ Connect to the PostgreSQL database server and run an sql command and print the results"""
+    conn = None
+    try:
+
+        print('Connecting to the PostgreSQL database...')
+        conn = psycopg2.connect( 
+                    host='localhost',
+                    database='PyCoders',
+                    user='postgres',
+                    password='0000'        )
+
+
+        conn.autocommit = True
+        cur = conn.cursor()
+
+
+        cur.execute(sql)
+
+
+        # return the command results :
+        result = cur.fetchall()
+        for r in result:
+            print (r)
+
+
+	# close the communication with the PostgreSQL
+        cur.close()
+    except (Exception, psycopg2.DatabaseError) as error:
+        print(error)
+    finally:
+        if conn is not None:
+            conn.close()
+            print('Database connection closed.')
+
+if __name__ == '__main__':
+   connect("CREATE TABLE IF NOT EXISTS students( student_id int  PRIMARY KEY , name varchar(50))")
+   connect("CREATE TABLE IF NOT EXISTS teachers( teacher_id int  PRIMARY KEY , name varchar(50))")
+   connect("INSERT INTO students (student_id , name) VALUES (1, 'Henry')")
+   connect("INSERT INTO students (student_id , name) VALUES (2, 'Y')")
+   connect("INSERT INTO students (student_id , name) VALUES (3, 'X')")
+   connect("INSERT INTO teachers (teacher_id , name) VALUES (1, 'John')")
+   connect("INSERT INTO teachers (teacher_id, name) VALUES (2, 'X')")
+   connect("INSERT INTO teachers (teacher_id, name) VALUES (3, 'Y')")
+
+   connect("SELECT * FROM students")
+   connect("SELECT * FROM teachers")

it_company.sql

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+-- This script was generated by a beta version of the ERD tool in pgAdmin 4.
+-- Please log an issue at https://redmine.postgresql.org/projects/pgadmin4/issues/new if you find any bugs, including reproduction steps.
+BEGIN;
+
+
+CREATE TABLE IF NOT EXISTS public.teams
+(
+    team_id integer,
+    product_id integer,
+    customer_id integer
+);
+
+CREATE TABLE IF NOT EXISTS public.responsibilitiy
+(
+    responsibilitiy_id integer NOT NULL,
+    title character varying(50),
+    PRIMARY KEY (responsibilitiy_id)
+);
+
+CREATE TABLE IF NOT EXISTS public.customers
+(
+    customer_id integer,
+    name character varying(55),
+    domain_id integer,
+    PRIMARY KEY (customer_id)
+);
+
+CREATE TABLE IF NOT EXISTS public.products
+(
+    product_id integer,
+    product_description text,
+    PRIMARY KEY (product_id)
+);
+
+CREATE TABLE IF NOT EXISTS public.employees
+(
+    member_id integer,
+    name character varying,
+    team_id integer,
+    responsibilitiy_id integer,
+    PRIMARY KEY (member_id)
+);
+
+CREATE TABLE IF NOT EXISTS public.domains
+(
+    domain_id integer,
+    domain_name character varying,
+    PRIMARY KEY (domain_id)
+);
+
+ALTER TABLE IF EXISTS public.teams
+    ADD FOREIGN KEY (product_id)
+    REFERENCES public.products (product_id) MATCH SIMPLE
+    ON UPDATE NO ACTION
+    ON DELETE NO ACTION
+    NOT VALID;
+
+
+ALTER TABLE IF EXISTS public.teams
+    ADD FOREIGN KEY (customer_id)
+    REFERENCES public.customers (customer_id) MATCH SIMPLE
+    ON UPDATE NO ACTION
+    ON DELETE NO ACTION
+    NOT VALID;
+
+
+ALTER TABLE IF EXISTS public.customers
+    ADD FOREIGN KEY (domain_id)
+    REFERENCES public.domains (domain_id) MATCH SIMPLE
+    ON UPDATE NO ACTION
+    ON DELETE NO ACTION
+    NOT VALID;
+
+
+ALTER TABLE IF EXISTS public.employees
+    ADD CONSTRAINT responsibilitiy FOREIGN KEY (responsibilitiy_id)
+    REFERENCES public.responsibilitiy (responsibilitiy_id) MATCH SIMPLE
+    ON UPDATE NO ACTION
+    ON DELETE NO ACTION
+    NOT VALID;
+
+
+ALTER TABLE IF EXISTS public.employees
+    ADD FOREIGN KEY (team_id)
+    REFERENCES public.teams (team_id) MATCH SIMPLE
+    ON UPDATE NO ACTION
+    ON DELETE NO ACTION
+    NOT VALID;
+
+END;