Workshop 3

Proect/DB_constraints.sql

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+/*
+    This block contains constraint creation,
+    such as FOREIGN KEYs, CHECKs etc.
+*/
+ALTER TABLE orders
+ADD CONSTRAINT check_orders_price
+CHECK (price > 0);
+
+ALTER TABLE comments
+ADD CONSTRAINT check_comment_rate
+CHECK (film_rate > 0);
+
+ALTER TABLE app_user
+ADD CONSTRAINT check_user_num
+CHECK (orders_num > 0);
+
+ALTER TABLE dish
+ADD CONSTRAINT check_dish_num
+CHECK (orders_num > 0);
+
+/*
+    ENDBLOCK
+*/

Proect/DB_triggers.sql

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+/*
+    This block dedicated to triggers
+*/
+/*
+    This sub-block contains group of triggers
+    that auto-generate ids for whole group of tables
+*/
+/*Comment table validation*/
+
+CREATE SEQUENCE pk1_seq
+    MINVALUE 1
+    START WITH 1
+    INCREMENT BY 1
+    CACHE 20;
+
+CREATE OR REPLACE TRIGGER pk_comment_id 
+BEFORE INSERT ON comments
+FOR EACH ROW
+WHEN ( new.comment_id IS NULL )
+BEGIN
+   :new.comment_id := pk1_seq.nextval;
+END;
+/
+/*App_user table validation*/
+
+CREATE SEQUENCE pk2_seq
+    MINVALUE 1
+    START WITH 1
+    INCREMENT BY 1
+    CACHE 20;
+
+CREATE OR REPLACE TRIGGER user_id_trigg 
+BEFORE INSERT ON app_user
+FOR EACH ROW
+WHEN ( new.user_id IS NULL )
+BEGIN
+    :new.user_id := pk2_seq.nextval;
+    IF :new.user_age < 0
+    THEN
+        raise_application_error(-20015,'User age is not valid!');
+    END IF;
+    IF :new.user_mail NOT LIKE '%@%.%'
+    THEN
+        raise_application_error(-20001,'User mail is not valid!');
+    END IF;
+    IF :new.user_phone NOT LIKE '+%'
+    THEN 
+        raise_application_error(-20003,'User phone number is not valid!');
+    END IF;
+    IF (LENGTH(TRIM(:new.user_bank)) > 19 OR LENGTH(TRIM(:new.user_bank)) < 13)
+    THEN 
+        raise_application_error(-20004,'User bank number is not valid!');
+    END IF;
+END;
+/
+
+
+/*Films table validation*/
+CREATE SEQUENCE pk6_seq
+    MINVALUE 1
+    START WITH 1
+    INCREMENT BY 1
+    CACHE 20;
+
+CREATE OR REPLACE TRIGGER pk_dish_id 
+BEFORE INSERT ON dishes
+FOR EACH ROW
+WHEN ( new.dishes_id IS NULL )
+BEGIN
+   :new.dish_id := pk6_seq.nextval;
+END;
+/
+
+/*Snack table validation*/
+CREATE SEQUENCE pk7_seq
+    MINVALUE 1
+    START WITH 1
+    INCREMENT BY 1
+    CACHE 20;
+
+CREATE OR REPLACE TRIGGER pk_snack_id 
+BEFORE INSERT ON snack
+FOR EACH ROW
+WHEN ( new.snack_id IS NULL )
+BEGIN
+   :new.snack_id := pk7_seq.nextval;
+END;
+/
+/*Orders table validation*/
+
+CREATE SEQUENCE pk3_seq
+    MINVALUE 1
+    START WITH 1
+    INCREMENT BY 1
+    CACHE 20;
+
+CREATE OR REPLACE TRIGGER order_trigg 
+BEFORE INSERT ON orders
+FOR EACH ROW
+WHEN ( new.order_id IS NULL )
+BEGIN
+    /*Updating number of orders while insert*/
+    UPDATE app_user
+    SET orders_num = (SELECT orders_num
+                      FROM app_user
+                      WHERE user_id = :new.user_id) + 1
+    WHERE user_id = :new.user_id;
+    UPDATE dishes
+    SET orders_num = (SELECT orders_num
+                      FROM dishes
+                      WHERE dish_id = :new.dish_id) + 1
+    WHERE diah_id = :new.film_id;
+
+    IF :new.snack_id IS NOT NULL
+    THEN
+        UPDATE snack
+        SET orders_num = (SELECT orders_num
+                          FROM snack
+                          WHERE snack_id = :new.snack_id) + 1
+        WHERE snack_id = :new.snack_id;
+    END IF;
+    :new.order_id := pk3_seq.nextval;
+END;
+/
+
+/*Ticket table validation*/
+CREATE SEQUENCE pk4_seq
+    MINVALUE 1
+    START WITH 1
+    INCREMENT BY 1
+    CACHE 20;
+
+
+CREATE OR REPLACE TRIGGER us_age 
+BEFORE INSERT ON orders
+FOR EACH ROW
+DECLARE
+    us_ag NUMBER(38,0);
+    v_age NUMBER(38,0);
+BEGIN
+    SELECT user_age INTO us_ag FROM app_user WHERE user_id = :new.user_id;
+    SELECT age_constraint INTO v_age FROM films WHERE film_id = :new.film_id;
+    IF (us_ag < v_age)
+    THEN raise_application_error(-20010,'User age is not valid');
+    END IF;
+END;
+/
+
+CREATE OR REPLACE TRIGGER user_age_apdate
+BEFORE UPDATE ON app_user
+FOR EACH ROW
+BEGIN
+    IF :old.user_age < :new.user_age
+    THEN 
+        raise_application_error(-20011,'User age cant be changed');
+    END IF;
+END;
+/
+/* 
+    END SUB-BLOCK
+*/
+
+/*
+    ANOUTHER SUB-BLOCKS IN PROGRESS
+*/
+/*
+    ENDBLOCK
+*/

Proect/OracleDb.py

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+import cx_Oracle
+import datetime
+from credentials import *
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+
+class OracleDb(object):
+    _instance = None
+
+    def __new__(cls):
+        if cls._instance is None:
+            cls._instance = object.__new__(cls)
+            try:
+                connection = cx_Oracle.connect(username, password, databaseName)
+                cursor = connection.cursor()
+
+                # execute a statement
+                cursor.execute('SELECT * FROM v$version')
+
+                # display the PostgreSQL database server version
+                db_version = cursor.fetchone()
+                print("New connection to {} created".format(db_version[0]))
+                oracle_connection_string = 'oracle+cx_oracle://{username}:{password}@{host}:{port}/{sid}'
+                engine = create_engine(oracle_connection_string.format(username="PMA_KM_20", password="oracle_2", sid="XE", host="localhost", port="1521", database="PMA_KM_20"))
+
+                Session = sessionmaker(bind=engine)
+                session = Session()
+
+                OracleDb._instance.sqlalchemy_session = session
+                OracleDb._instance.sqlalchemy_engine = engine
+                OracleDb._instance.connection = connection
+                OracleDb._instance.cursor = cursor
+
+            except Exception as error:
+                print('Error: connection not established {}'.format(error))
+
+        return cls._instance
+
+    def __init__(self):
+        oracle_connection_string = 'oracle+cx_oracle://{username}:{password}@{host}:{port}/{sid}'
+        engine = create_engine(oracle_connection_string.format(username=username, password=password, sid=service_name, host=ip, port=port, database=databaseName))
+
+        Session = sessionmaker(bind=engine)
+        session = Session()
+
+        self.sqlalchemy_session = session
+        self.sqlalchemy_engine = engine
+        self.connection = self._instance.connection
+        self.cursor = self._instance.cursor
+
+    def execute(self, query):
+        '''
+        Функція, що дозволяє робити
+        запити з бд
+        '''
+        try:
+            result = self.cursor.execute(query)
+            self.connection.commit()
+        except Exception as error:
+            print('error execting query "{}", error: {}'.format(query, error))
+            return None
+        else:
+            return result
+
+    def __del__(self):
+        self.sqlalchemy_session.close()
+
+
+if __name__ == "__main__":
+    # створюємо екземпляр класу ОраклДб
+    db = OracleDb()

Proect/credentials.py

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+import cx_Oracle
+
+username = 'PMA_KM_20'
+password = 'oracle_2'
+ip = 'localhost'
+port = 1521
+service_name = 'XE'
+dsn = cx_Oracle.makedsn(ip, port, service_name=service_name)
+databaseName = dsn
+
+DIALECT = 'oracle'
+SQL_DRIVER = 'cx_oracle'
+USERNAME = 'PMA_KM_20'
+PASSWORD = 'oracle_2'
+
+HOST = 'localhost'
+PORT = 1521
+SERVICE = 'orcl'
+
+ENGINE_PATH_WIN_AUTH = DIALECT + '+' + SQL_DRIVER + '://' + USERNAME + ':' + PASSWORD +'@' + HOST + ':' + str(PORT) + '/?service_name=' + SERVICE