TITLE: UofT-DSI | SQL - Assignment 2

02_activities/assignments/assignment2.sql

@@ -20,7 +20,11 @@ The `||` values concatenate the columns into strings.
 Edit the appropriate columns -- you're making two edits -- and the NULL rows will be fixed. 
 All the other rows will remain the same.) */
 
+SELECT *
+,ifnull (product_name, 'unknown')
+,coalesce (product_size, 'unit')
 
+FROM product;
 
 --Windowed Functions
 /* 1. Write a query that selects from the customer_purchases table and numbers each customer’s  
@@ -32,21 +36,31 @@ each new market date for each customer, or select only the unique market dates p
 (without purchase details) and number those visits. 
 HINT: One of these approaches uses ROW_NUMBER() and one uses DENSE_RANK(). */
 
-
+SELECT DISTINCT customer_id, market_date, DENSE_RANK() OVER (
+     PARTITION BY customer_id
+     ORDER BY market_date ASC
+) AS visit
+FROM customer_purchases;
 
 /* 2. Reverse the numbering of the query from a part so each customer’s most recent visit is labeled 1, 
 then write another query that uses this one as a subquery (or temp table) and filters the results to 
 only the customer’s most recent visit. */
 
-
+SELECT DISTINCT customer_id, market_date, DENSE_RANK() OVER (
+     PARTITION BY customer_id
+     ORDER BY market_date DESC
+) AS visit
+FROM customer_purchases;
 
 /* 3. Using a COUNT() window function, include a value along with each row of the 
 customer_purchases table that indicates how many different times that customer has purchased that product_id. */
 
-
+SELECT *,
+COUNT (*) OVER (PARTITION BY customer_id, product_id) as times_bought
+FROM customer_purchases;
 
 -- String manipulations
-/* 1. Some product names in the product table have descriptions like "Jar" or "Organic". 
+/* 1. Some product names in the product table have descriptions like "Jar" or "Organic". 
 These are separated from the product name with a hyphen. 
 Create a column using SUBSTR (and a couple of other commands) that captures these, but is otherwise NULL. 
 Remove any trailing or leading whitespaces. Don't just use a case statement for each product! 
@@ -61,6 +75,15 @@ Hint: you might need to use INSTR(product_name,'-') to find the hyphens. INSTR w
 
 /* 2. Filter the query to show any product_size value that contain a number with REGEXP. */
 
+SELECT product_name,
+CASE 
+   WHEN INSTR (product_name, '-')  THEN 
+      SUBSTR (product_name,  RTRIM(LTRIM(INSTR(product_name, '-') + 1))) 
+   ELSE NULL
+END
+AS discription
+FROM product;
+
 
 
 -- UNION
@@ -73,8 +96,20 @@ HINT: There are a possibly a few ways to do this query, but if you're struggling
 3) Query the second temp table twice, once for the best day, once for the worst day, 
 with a UNION binding them. */
 
-
-
+WITH sales_table  AS (
+	SELECT  market_date, SUM(quantity * cost_to_customer_per_qty)  AS sales
+	FROM customer_purchases
+	GROUP BY market_date
+),
+days_ranked_table AS (
+    SELECT market_date, sales,
+	   RANK () OVER (ORDER BY sales ASC) as rank_asc,
+	   RANK () OVER (ORDER BY sales DESC) as rank_desc
+	 FROM sales_table
+)
+SELECT market_date, sales FROM days_ranked_table WHERE rank_desc == 1
+UNION ALL
+SELECT market_date, sales FROM days_ranked_table WHERE rank_asc == 1;
 
 /* SECTION 3 */
 
@@ -89,28 +124,40 @@ Think a bit about the row counts: how many distinct vendors, product names are t
 How many customers are there (y). 
 Before your final group by you should have the product of those two queries (x*y).  */
 
+/* 
+sorry this qeustion was too ambigous for me :( I dont know how to find out:
 
+1) which products a vendor offers; is this just ones that have inventory?
+2) what the price of a product is; is this just last original_price paid for that product by date???
+*/
 
 -- INSERT
 /*1.  Create a new table "product_units". 
 This table will contain only products where the `product_qty_type = 'unit'`. 
 It should use all of the columns from the product table, as well as a new column for the `CURRENT_TIMESTAMP`.  
 Name the timestamp column `snapshot_timestamp`. */
 
-
+DROP TABLE IF EXISTS product_units;
+CREATE TABLE product_units AS
+	SELECT *, CURRENT_TIMESTAMP AS snapshot_timestamp FROM product
+	WHERE product_qty_type = 'unit';
 
 /*2. Using `INSERT`, add a new row to the product_units table (with an updated timestamp). 
 This can be any product you desire (e.g. add another record for Apple Pie). */
 
-
+INSERT INTO product_units
+VALUES (7, 'Apple Pie', '10"', 3, 'unit', CURRENT_TIMESTAMP);
 
 -- DELETE
 /* 1. Delete the older record for the whatever product you added. 
 
 HINT: If you don't specify a WHERE clause, you are going to have a bad time.*/
 
-
-
+DELETE FROM product_units
+WHERE product_name = 'Apple Pie'
+  AND snapshot_timestamp < (
+    SELECT MAX(snapshot_timestamp) FROM product_units WHERE product_name = 'Apple Pie');
+
 -- UPDATE
 /* 1.We want to add the current_quantity to the product_units table. 
 First, add a new column, current_quantity to the table using the following syntax.
@@ -128,6 +175,32 @@ Finally, make sure you have a WHERE statement to update the right row,
 	you'll need to use product_units.product_id to refer to the correct row within the product_units table. 
 When you have all of these components, you can run the update statement. */
 
+ALTER TABLE product_units
+ADD current_quantity INT;
 
-
-
+-- Get last quantity per vendor per product
+WITH current_quantity_per_vendor_table AS (
+	SELECT  product_id, vendor_id, quantity, market_date,
+		RANK()  OVER (PARTITION BY product_id,vendor_id ORDER BY market_date DESC) AS last
+	FROM vendor_inventory
+),
+-- Reduce final quantities across vendors
+current_quantity_table AS (
+	SELECT product_id, SUM(quantity) AS current_quantity
+	FROM current_quantity_per_vendor_table
+	WHERE last == 1
+	GROUP BY product_id
+) ,
+product_units_with_quantity AS (
+  -- keep all product_units rows; fill missing with 0
+  SELECT
+    product_id,
+    COALESCE(current_quantity_table.current_quantity, 0) AS current_quantity
+  FROM product_units 
+  LEFT JOIN current_quantity_table USING (product_id)
+)
+-- update counts
+UPDATE product_units 
+    SET current_quantity =  product_units_with_quantity.current_quantity
+	FROM product_units_with_quantity
+	WHERE product_units_with_quantity.product_id == product_units.product_id;</sql><current_tab id="3"/></tab_sql></sqlb_project>