made exercises

How-to-code-subqueries.sql

@@ -1,60 +1,72 @@
-SELECT DISTINCT category_name
-FROM categories
-	WHERE category_id IN (SELECT category_id FROM products)
-ORDER BY category_name;
-
-SELECT product_name, list_price
-FROM products
-	WHERE list_price > (SELECT AVG(list_price) FROM products)
-ORDER BY list_price DESC;
-
-SELECT category_name
-FROM categories
-WHERE NOT EXISTS (SELECT * FROM products
-	WHERE category_id = categories.category_id);
-
-SELECT email_address,
-	i.order_id,
-	SUM((i.item_price - i.discount_amount) * quantity) AS 'order_total'
-FROM customers c JOIN orders o
-		ON c.customer_id = o.customer_id
-    JOIN order_items i
-		ON o.order_id = i.order_id
-GROUP BY email_address, order_id;
-
-SELECT email_address,
-	MAX(order_total)
-FROM (SELECT email_address,
-	i.order_id,
-	SUM((i.item_price - i.discount_amount) * quantity) AS 'order_total'
-FROM customers c JOIN orders o
-		ON c.customer_id = o.customer_id
-	JOIN order_items i
-		ON o.order_id = i.order_id
-GROUP BY email_address, order_id) f
-GROUP BY email_address;
-
-SELECT product_name,
-	discount_percent
-FROM products
-WHERE discount_percent NOT IN (SELECT discount_percent
-	FROM products
-	GROUP BY discount_percent
-	HAVING COUNT(discount_percent) > 1)
-ORDER BY product_name;
-
-SELECT email_address,
-	order_id,
-	order_date
-FROM customers c JOIN orders o
-	ON c.customer_id = o.customer_id
-WHERE order_date = (SELECT MIN(order_date)
-	FROM orders
-	WHERE customer_id = o.customer_id);
+    -- Exercise 1
+
+    SELECT category_name
+    FROM categories
+    WHERE category_id IN (SELECT DISTINCT category_id
+    						FROM products)
+    ORDER BY category_name;
+
+    -- Exercise 2
+
+    SELECT product_name,
+    	list_price
+    FROM products
+    WHERE list_price > (SELECT AVG(list_price)
+    					FROM products)
+    ORDER BY list_price DESC;
+
+    -- Exercise 3
+
+    SELECT category_name
+    FROM categories
+    WHERE NOT EXISTS (SELECT *
+    					FROM products
+                        WHERE category_id = categories.category_id);
+
+    -- Exercise 4
+
+    SELECT email_address,
+    	i.order_id,
+    	SUM((i.item_price - i.discount_amount) * quantity) AS 'order_total'
+    FROM customers c JOIN orders o
+    		ON c.customer_id = o.customer_id
+        JOIN order_items i
+    		ON o.order_id = i.order_id
+    GROUP BY email_address, order_id;
+
+    -- Exercise 4 Part 2
+
+    SELECT email_address,
+    	MAX(order_total)
+    FROM (SELECT email_address,
+    	i.order_id,
+    	SUM((i.item_price - i.discount_amount) * quantity) AS 'order_total'
+    FROM customers c JOIN orders o
+    		ON c.customer_id = o.customer_id
+        JOIN order_items i
+    		ON o.order_id = i.order_id
+    GROUP BY email_address, order_id) f
+    GROUP BY email_address;
+
+    -- Exercise 5
+
+    SELECT product_name,
+    	discount_percent
+    FROM products
+    WHERE discount_percent NOT IN (SELECT
+    						discount_percent
+    					FROM products
+                        GROUP BY discount_percent
+                        HAVING COUNT(discount_percent) > 1)
+    ORDER BY product_name;
+
+    -- Exercise 6
+
+    SELECT email_address,
+    	order_id,
+    	order_date
+    FROM customers c JOIN orders o
+    	ON c.customer_id = o.customer_id
+    WHERE order_date = (SELECT MIN(order_date)
+    					FROM orders
+    					WHERE customer_id = o.customer_id);