Help: How to write a query formula?

Question

Problem. There are 4 tables of a database of a store:
Table 1: Tarifs
Columns: Tarif_number, Price
Primary key: Tarif_number
Table 2: Products
Columns: Product_number, Product_name, Quantity;
Primary key: Product_number
Data: Tarif 1 - 100%, Tarif 2 - 75 %, Tarif 3 - 50 %, Tarif 4 - 25 % (discounts)
Table 3: Customers
Columns: Customer_Number, Customer_Name, Address, Phone;
Primary Key: Client_Number
Table 4: Sales
Columns: Date, Product_Number, Tarif_Number, Quantity_Sold, Customer_Name
Primary key: Date, Product_Number, Customer_Number, Tarif_Number
The problem is to write SQL PLUS queries, which would bring the following results:
i. Data off all customers (name, address, phone), who within the period from 3/4/2009 to 4/4/2009 purchased products containing the string "abc" in its name. The data should be arranged alphabetically by product name. The report should have a footnote including name of its author.
ii which product was purchased the most frequently and the total purchase value. The footnote should include the title and the date of the printout.
iii Catalogue product number, product name, quantity on store, quantity sold for any product in the database. The product name should be introduced from keyboard in order to make possible to enter this or similar query later.

Answer 1

Queries not tested*
I) SELECT cs.customer_name, cs.address, cs.phone
FROM customers cs, sales sl, products prd
WHERE cs.customer_number = sl.customer_number
AND prd.product_number = sl.product_number
AND sl.DATE BETWEEN TO_DATE ('3/4/2009', 'DD/MM/YYYY')
AND TO_DATE ('4/4/2009', 'DD/MM/YYYY')
AND LOWER (prd.product_name) LIKE '%abc%'
II) SELECT prd.product_name, SUM (sl.quantity_sold * tf.price)
FROM sales sl, product prd, tarifs tf
WHERE sl.product_number = prd.product_number
AND tf.tarif_number = sl.tarif_number
GROUP BY sl.product_number
HAVING COUNT (1) = (SELECT MAX (COUNT (1))
FROM sales sl1
GROUP BY sl1.product_number)
III) SELECT prd.product_name, prd.quantity, SUM (sl.quantity_sold)
FROM sales sl, product prd, tarifs tf
WHERE sl.product_number = prd.product_number
AND tf.tarif_number = sl.tarif_number
GROUP BY sl.product_number