Need help on setting up database star schema and the queries

DROP TABLE ORDER_ITEMS; DROP TABLE ORDERS; DROP TABLE CUSTOMERS; DROP TABLE PRODUCTS; DROP TABLE CATEGORIES; CREATE TABLE CATEGORIES ( ID NUMBER PRIMARY KEY, Name VARCHAR2(20) NOT NULL); CREATE TABLE PRODUCTS ( ID NUMBER PRIMARY KEY, CatID NUMBER, Name VARCHAR2(20) NOT NULL, Price NUMBER NOT NULL, FOREIGN KEY (CatID) REFERENCES CATEGORIES(ID)); CREATE TABLE CUSTOMERS ( ID NUMBER PRIMARY KEY, Name VARCHAR2(50) NOT NULL, DOB DATE NOT NULL, Email VARCHAR2(50), ZipCode CHAR(5) NOT NULL); CREATE TABLE ORDERS ( ID NUMBER PRIMARY KEY, CustID NUMBER NOT NULL, DatePlaced DATE DEFAULT SYSDATE, FOREIGN KEY (CustID) REFERENCES CUSTOMERS(ID)); CREATE TABLE ORDER_ITEMS ( OrderID NUMBER NOT NULL, ProdID NUMBER NOT NULL, Quantity NUMBER DEFAULT 1, DateShipped DATE, FOREIGN KEY (OrderID) REFERENCES ORDERS(ID), FOREIGN KEY (ProdID) REFERENCES PRODUCTS(ID)); INSERT INTO CATEGORIES VALUES (1, 'Books'); INSERT INTO CATEGORIES VALUES (2, 'Electronics'); INSERT INTO CATEGORIES VALUES (3, 'Outdoors'); INSERT INTO PRODUCTS VALUES (1, 1, 'The Lost Years', 15); INSERT INTO PRODUCTS VALUES (2, 1, 'iPhone Development', 24); INSERT INTO PRODUCTS VALUES (3, 1, 'A Raisin in the Sun', 11); INSERT INTO PRODUCTS VALUES (4, 1, 'Lone Wolf', 17); INSERT INTO PRODUCTS VALUES (5, 1, 'Harry Potter', 50); INSERT INTO PRODUCTS VALUES (6, 2, 'USB Flash Drive', 25); INSERT INTO PRODUCTS VALUES (7, 2, 'Laptop Mouse', 35); INSERT INTO PRODUCTS VALUES (8, 2, 'Laser Printer', 250); INSERT INTO PRODUCTS VALUES (9, 2, 'Speaker System', 65); INSERT INTO PRODUCTS VALUES (10, 2, 'Broadband Router', 75); INSERT INTO PRODUCTS VALUES (11, 3, 'Student Backpack', 35); INSERT INTO PRODUCTS VALUES (12, 3, 'Flash Light', 80); INSERT INTO PRODUCTS VALUES (13, 3, 'Men''s Jacket', 99); INSERT INTO PRODUCTS VALUES (14, 3, 'Binocular', 60); INSERT INTO PRODUCTS VALUES (15, 3, 'Swiss Army Knife', 20); INSERT INTO CUSTOMERS VALUES (1, 'John M. Newton', '11-JAN-1980', '[email protected]', 21001); INSERT INTO CUSTOMERS VALUES (2, 'David S. Harrington', '21-JUL-1985', '[email protected]', 21002); INSERT INTO CUSTOMERS VALUES (3, 'Bob R. Hume', '21-JAN-1990', '[email protected]', 21003); INSERT INTO CUSTOMERS VALUES (4, 'Jeff A. Newman', '12-FEB-1975', '[email protected]', 21004); INSERT INTO CUSTOMERS VALUES (5, 'Bill G. Davidson', '21-DEC-1989', '[email protected]', 21005); INSERT INTO CUSTOMERS VALUES (6, 'Joe A. Huntsman', '10-MAR-1965', '[email protected]', 21006); INSERT INTO CUSTOMERS VALUES (7, 'Chris W. White', '22-MAR-1955', '[email protected]', 21007); INSERT INTO CUSTOMERS VALUES (8, 'Mark A. Black', '13-JAN-1973', '[email protected]', 21008); INSERT INTO CUSTOMERS VALUES (9, 'Vlad B. Johnson', '16-DEC-1997', '[email protected]', 21009); INSERT INTO CUSTOMERS VALUES (10, 'Matt C. Allen', '04-OCT-1977', '[email protected]', 21010); INSERT INTO ORDERS VALUES (1, 1, '25-MAR-2015'); INSERT INTO ORDER_ITEMS VALUES (1, 1, 2, '25-MAR-2015'); INSERT INTO ORDER_ITEMS VALUES (1, 3, 1, '25-MAR-2015'); INSERT INTO ORDER_ITEMS VALUES (1, 5, 3, '25-MAR-2015'); INSERT INTO ORDER_ITEMS VALUES (1, 9, 2, '25-MAR-2015'); INSERT INTO ORDERS VALUES (2, 2, '26-MAR-2015'); INSERT INTO ORDER_ITEMS VALUES (2, 11, 1, '27-MAR-2015'); INSERT INTO ORDER_ITEMS VALUES (2, 13, 4, '27-MAR-2015'); INSERT INTO ORDER_ITEMS VALUES (2, 15, 2, '27-MAR-2015'); INSERT INTO ORDERS VALUES (3, 3, '27-MAR-2015'); INSERT INTO ORDER_ITEMS VALUES (3, 2, 1, '28-MAR-2015'); INSERT INTO ORDER_ITEMS VALUES (3, 4, 1, '28-MAR-2015'); INSERT INTO ORDER_ITEMS VALUES (3, 14, 2, '28-MAR-2015'); INSERT INTO ORDER_ITEMS VALUES (3, 7, 2, NULL); INSERT INTO ORDERS VALUES (13, 3, '07-APR-2015'); INSERT INTO ORDER_ITEMS VALUES (13, 12, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (13, 14, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (13, 8, 1, NULL); INSERT INTO ORDERS VALUES (4, 5, '28-MAR-2015'); INSERT INTO ORDER_ITEMS VALUES (4, 5, 2, '29-MAR-2015'); INSERT INTO ORDER_ITEMS VALUES (4, 8, 2, '29-MAR-2015'); INSERT INTO ORDER_ITEMS VALUES (4, 6, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (4, 12, 1, NULL); INSERT INTO ORDERS VALUES (14, 4, '08-AUG-2014'); INSERT INTO ORDER_ITEMS VALUES (14, 2, 1, '29-AUG-2014'); INSERT INTO ORDER_ITEMS VALUES (14, 10, 2, '29-AUG-2014'); INSERT INTO ORDER_ITEMS VALUES (14, 6, 3, NULL); INSERT INTO ORDER_ITEMS VALUES (14, 9, 2, NULL); INSERT INTO ORDERS VALUES (5, 6, '18-APR-2015'); INSERT INTO ORDER_ITEMS VALUES (5, 1, 2, NULL); INSERT INTO ORDER_ITEMS VALUES (5, 3, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (5, 15, 3, NULL); INSERT INTO ORDER_ITEMS VALUES (5, 5, 4, NULL); INSERT INTO ORDERS VALUES (6, 6, '01-APR-2015'); INSERT INTO ORDER_ITEMS VALUES (6, 11, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (6, 13, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (6, 5, 2, NULL); INSERT INTO ORDER_ITEMS VALUES (6, 7, 1, NULL); INSERT INTO ORDERS VALUES (7, 7, '07-SEP-2014'); INSERT INTO ORDER_ITEMS VALUES (7, 1, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (7, 2, 2, NULL); INSERT INTO ORDER_ITEMS VALUES (7, 9, 1, NULL); INSERT INTO ORDERS VALUES (8, 7, '07-OCT-2014'); INSERT INTO ORDER_ITEMS VALUES (8, 4, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (8, 8, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (8, 14, 1, NULL); INSERT INTO ORDERS VALUES (9, 2, '14-NOV-2014'); INSERT INTO ORDER_ITEMS VALUES (9, 13, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (9, 3, 2, NULL); INSERT INTO ORDER_ITEMS VALUES (9, 5, 1, NULL); INSERT INTO ORDERS VALUES (10, 8, '24-DEC-2014'); INSERT INTO ORDER_ITEMS VALUES (10, 15, 3, NULL); INSERT INTO ORDER_ITEMS VALUES (10, 1, 2, NULL); INSERT INTO ORDER_ITEMS VALUES (10, 9, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (10, 8, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (10, 11, 1, NULL); INSERT INTO ORDERS VALUES (11, 8, '04-JAN-2015'); INSERT INTO ORDER_ITEMS VALUES (11, 15, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (11, 12, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (11, 5, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (11, 2, 3, NULL); INSERT INTO ORDER_ITEMS VALUES (11, 6, 1, NULL); INSERT INTO ORDERS VALUES (12, 9, '24-DEC-2014'); INSERT INTO ORDER_ITEMS VALUES (12, 1, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (12, 7, 2, NULL); INSERT INTO ORDER_ITEMS VALUES (12, 9, 4, NULL); INSERT INTO ORDER_ITEMS VALUES (12, 12, 3, NULL); INSERT INTO ORDERS VALUES (15, 10, '05-NOV-2013'); INSERT INTO ORDER_ITEMS VALUES (15, 13, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (15, 7, 2, NULL); INSERT INTO ORDER_ITEMS VALUES (15, 8, 1, NULL); INSERT INTO ORDER_ITEMS VALUES (15, 2, 1, NULL);