-- Customer by Order --
SELECT distinct c.CUSTOMER_ID , initcap(C.CUST_FIRST_NAME || ' ' || C.CUST_LAST_NAME)  Name, o.ORDER_ID, O.ORDER_TOTAL  
FROM DEMO_CUSTOMERS C, DEMO_ORDERS O, DEMO_ORDER_ITEMS I
where C.CUSTOMER_ID   = O.CUSTOMER_ID   and
      I.ORDER_ID = O.ORDER_ID

-- Customer by Product --
SELECT distinct c.CUSTOMER_ID , initcap(C.CUST_FIRST_NAME || ' ' || C.CUST_LAST_NAME)  Name, p.product_id, P.PRODUCT_DESCRIPTION  
FROM DEMO_CUSTOMERS C, DEMO_ORDERS O, DEMO_ORDER_ITEMS I,  DEMO_PRODUCT_INFO P
where C.CUSTOMER_ID (+)  = O.CUSTOMER_ID   and
      I.ORDER_ID = O.ORDER_ID and
      I.PRODUCT_ID = p.product_id

-- Customer by Order and Product --
SELECT distinct c.CUSTOMER_ID , initcap(C.CUST_FIRST_NAME || ' ' || C.CUST_LAST_NAME)  Name, i.order_item_id,  p.product_id, P.PRODUCT_DESCRIPTION  
FROM DEMO_CUSTOMERS C, DEMO_ORDERS O, DEMO_ORDER_ITEMS I,  DEMO_PRODUCT_INFO P
where C.CUSTOMER_ID (+)  = O.CUSTOMER_ID   and
      I.ORDER_ID = O.ORDER_ID and
      I.PRODUCT_ID = p.product_id (+)

-- Customer By Order & Non Order --
SELECT c.CUSTOMER_ID,  initcap(C.CUST_FIRST_NAME || ' ' || C.CUST_LAST_NAME)  Name,  min(O.ORDER_ID) Order_id
FROM DEMO_CUSTOMERS C, DEMO_ORDERS O
where C.CUSTOMER_ID  = O.CUSTOMER_ID (+)
        group by c.CUSTOMER_ID, C.CUST_FIRST_NAME, C.CUST_LAST_NAME order by c.customer_id