/* Screen 3 */
-- Table descriptions
SELECT 'Customers' AS table_name, 
       13 AS number_of_attribute,
       COUNT(*) AS number_of_row
  FROM Customers
  
UNION ALL

SELECT 'Products' AS table_name, 
       9 AS number_of_attribute,
       COUNT(*) AS number_of_row
  FROM Products

UNION ALL

SELECT 'ProductLines' AS table_name, 
       4 AS number_of_attribute,
       COUNT(*) AS number_of_row
  FROM ProductLines

UNION ALL

SELECT 'Orders' AS table_name, 
       7 AS number_of_attribute,
       COUNT(*) AS number_of_row
  FROM Orders

UNION ALL

SELECT 'OrderDetails' AS table_name, 
       5 AS number_of_attribute,
       COUNT(*) AS number_of_row
  FROM OrderDetails

UNION ALL

SELECT 'Payments' AS table_name, 
       4 AS number_of_attribute,
       COUNT(*) AS number_of_row
  FROM Payments

UNION ALL

SELECT 'Employees' AS table_name, 
       8 AS number_of_attribute,
       COUNT(*) AS number_of_row
  FROM Employees

UNION ALL

SELECT 'Offices' AS table_name, 
       9 AS number_of_attribute,
       COUNT(*) AS number_of_row
  FROM Offices;

/* Screen 4 */
--Low stock
SELECT productCode, 
       ROUND(SUM(quantityOrdered) * 1.0 / (SELECT quantityInStock
                                             FROM products p
                                            WHERE od.productCode = p.productCode), 2) AS low_stock
  FROM orderdetails od
 GROUP BY productCode
 ORDER BY low_stock DESC
 LIMIT 10;
 

-- Product performance
SELECT productCode, 
       SUM(quantityOrdered * priceEach) AS prod_perf
  FROM orderdetails od
 GROUP BY productCode 
 ORDER BY prod_perf DESC
 LIMIT 10;
 
-- Priority Products for restocking
WITH 

low_stock_table AS (
SELECT productCode, 
       ROUND(SUM(quantityOrdered) * 1.0/(SELECT quantityInStock
                                           FROM products p
                                          WHERE od.productCode = p.productCode), 2) AS low_stock
  FROM orderdetails od
 GROUP BY productCode
 ORDER BY low_stock DESC
 LIMIT 10
)

SELECT productCode, 
       SUM(quantityOrdered * priceEach) AS prod_perf
  FROM orderdetails od
 WHERE productCode IN (SELECT productCode
                         FROM low_stock_table)
 GROUP BY productCode 
 ORDER BY prod_perf DESC
 LIMIT 10;


/* Screen 5 */
-- revenue by customer
SELECT o.customerNumber, SUM(quantityOrdered * (priceEach - buyPrice)) AS revenue
  FROM products p
  JOIN orderdetails od
    ON p.productCode = od.productCode
  JOIN orders o
    ON o.orderNumber = od.orderNumber
 GROUP BY o.customerNumber;
 
-- Top 5 VIP customers
WITH 

money_in_by_customer_table AS (
SELECT o.customerNumber, SUM(quantityOrdered * (priceEach - buyPrice)) AS revenue
  FROM products p
  JOIN orderdetails od
    ON p.productCode = od.productCode
  JOIN orders o
    ON o.orderNumber = od.orderNumber
 GROUP BY o.customerNumber
)

SELECT contactLastName, contactFirstName, city, country, mc.revenue
  FROM customers c
  JOIN money_in_by_customer_table mc
    ON mc.customerNumber = c.customerNumber
 ORDER BY mc.revenue DESC
 LIMIT 5;
 
 -- Top 5 less engaging customers
WITH 

money_in_by_customer_table AS (
SELECT o.customerNumber, SUM(quantityOrdered * (priceEach - buyPrice)) AS revenue
  FROM products p
  JOIN orderdetails od
    ON p.productCode = od.productCode
  JOIN orders o
    ON o.orderNumber = od.orderNumber
 GROUP BY o.customerNumber
)

SELECT contactLastName, contactFirstName, city, country, mc.revenue
  FROM customers c
  JOIN money_in_by_customer_table mc
    ON mc.customerNumber = c.customerNumber
 ORDER BY mc.revenue
 LIMIT 5;
 
-- Customer LTV
WITH 

money_in_by_customer_table AS (
SELECT o.customerNumber, SUM(quantityOrdered * (priceEach - buyPrice)) AS revenue
  FROM products p
  JOIN orderdetails od
    ON p.productCode = od.productCode
  JOIN orders o
    ON o.orderNumber = od.orderNumber
 GROUP BY o.customerNumber
)

SELECT AVG(mc.revenue) AS ltv
  FROM money_in_by_customer_table mc;