Changes between Initial Version and Version 1 of AdvancedReport7

Timestamp:

08/21/26 05:56:29 (29 hours ago)

Author:

235018

Comment:

--

AdvancedReport7

@@ +1 @@
+= Products ordered by number of orders from highest to lowest
+{{{#!sql
+CREATE OR REPLACE FUNCTION get_products_by_number_of_orders()
+RETURNS TABLE (
+    product_code INT,
+    product_description TEXT,
+    product_price NUMERIC,
+    number_of_orders BIGINT
+)
+LANGUAGE plpgsql
+AS $$
+BEGIN
+    RETURN QUERY
+    SELECT
+        p.code AS product_code,
+        p.description AS product_description,
+        p.price AS product_price,
+        COUNT(DISTINCT o.order_num) AS number_of_orders
+    FROM product p
+    JOIN includes i
+        ON p.code = i.code
+    JOIN "order" o
+        ON i.order_num = o.order_num
+    GROUP BY
+        p.code,
+        p.description,
+        p.price
+    ORDER BY
+        number_of_orders DESC;
+END;
+$$;
+
+}}}
+
+== Relational Algebra
+- P(code, price, availability, description, ...)
+- O(order_num, quantity, status, last_modified_date, payment_method, discount)
+- I(code, order_num)
+
+**JOIN products with orders:**
+- J1 ← P ⟕P.code = I.code I
+- J2 ← J1 ⟕I.order_num = O.order_num O
+
+**Calculate the number of distinct orders the product has been in:**
+- R ← γcode, description, price;
+     COUNT(DISTINCT order_num) → number_of_orders
+     (J2)
+
+**Sort by total orders:**
+- R_final ← τnumber_of_orders DESC(R)
+
+