Assignment two

02_activities/assignments/Cohort_8/Assignment2.md

@@ -54,7 +54,8 @@ The store wants to keep customer addresses. Propose two architectures for the CU
 **HINT:** search type 1 vs type 2 slowly changing dimensions. 
 
 ```
-Your answer...
+CUSTOMER_ADDRESS_TYPE1 keeps one current row per customer. Updates overwrite prior values. It can keep the table simple, always current, but there is no history that we can search.
+CUSTOMER_ADDRESS_TYPE2 stores multiple rows per customer with the start and end date, effective boolean. It gives the full history, but will need more complex queries and database storage.
 ```
 
 ***

02_activities/assignments/Cohort_8/assignment2.sql

@@ -20,8 +20,19 @@ nulls, and 'unit' for the second column with nulls.
 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 *
+FROM product
+WHERE product_size IS NULL
+   OR product_qty_type IS NULL;
 
-
+SELECT
+  product_name
+  || ', '
+  || COALESCE(product_size, '')
+  || ' ('
+  || COALESCE(product_qty_type, 'unit')
+  || ')' AS product_list
+FROM product;
 
 
 --Windowed Functions
@@ -34,16 +45,43 @@ 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
+  cp.*,
+  DENSE_RANK() OVER (
+    PARTITION BY cp.customer_id
+    ORDER BY cp.market_date
+  ) AS visit_number
+FROM customer_purchases cp;
 
 
 /* 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. */
-
+WITH ranked AS (
+  SELECT
+    customer_id,
+    market_date,
+    DENSE_RANK() OVER (
+      PARTITION BY customer_id
+      ORDER BY market_date DESC
+    ) AS rev_visit_number
+  FROM customer_purchases
+  GROUP BY customer_id, market_date
+)
+SELECT customer_id, market_date
+FROM ranked
+WHERE rev_visit_number = 1
+ORDER BY customer_id;
 
 
 /* 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
+  cp.*,
+  COUNT(*) OVER (
+    PARTITION BY customer_id, product_id
+  ) AS times_bought
+FROM customer_purchases cp;
 
 
 
@@ -58,11 +96,19 @@ Remove any trailing or leading whitespaces. Don't just use a case statement for
 | Habanero Peppers - Organic | Organic     |
 
 Hint: you might need to use INSTR(product_name,'-') to find the hyphens. INSTR will help split the column. */
-
-
+SELECT
+  product_name,
+  CASE
+    WHEN INSTR(product_name, '-') > 0
+      THEN TRIM(SUBSTR(product_name, INSTR(product_name, '-') + 1))
+  END AS description
+FROM product;
 
 /* 2. Filter the query to show any product_size value that contain a number with REGEXP. */
 
+SELECT *
+FROM product
+WHERE product_size REGEXP '[0-9]';
 
 
 -- UNION
@@ -76,6 +122,28 @@ HINT: There are a possibly a few ways to do this query, but if you're struggling
 with a UNION binding them. */
 
 
+WITH sales_by_date AS (
+  SELECT
+    market_date,
+    ROUND(SUM(quantity * cost_to_customer_per_qty), 2) AS total_sales
+  FROM customer_purchases
+  GROUP BY market_date
+),
+ranked AS (
+  SELECT
+    market_date,
+    total_sales,
+    RANK() OVER (ORDER BY total_sales DESC) AS r_desc,
+    RANK() OVER (ORDER BY total_sales ASC)  AS r_asc
+  FROM sales_by_date
+)
+SELECT 'best_day' AS tag, market_date, total_sales
+FROM ranked
+WHERE r_desc = 1
+UNION ALL
+SELECT 'worst_day' AS tag, market_date, total_sales
+FROM ranked
+WHERE r_asc = 1;
 
 
 /* SECTION 3 */
@@ -90,7 +158,37 @@ Remember, CROSS JOIN will explode your table rows, so CROSS JOIN should likely b
 Think a bit about the row counts: how many distinct vendors, product names are there (x)?
 How many customers are there (y). 
 Before your final group by you should have the product of those two queries (x*y).  */
-
+WITH latest_price AS (           
+  SELECT vendor_id, product_id, original_price
+  FROM (
+    SELECT vi.*,
+           ROW_NUMBER() OVER (
+             PARTITION BY vendor_id, product_id
+             ORDER BY market_date DESC
+           ) AS rn
+    FROM vendor_inventory vi
+  ) t
+  WHERE rn = 1
+),
+cust AS (                        
+  SELECT COUNT(*) AS customers FROM customer
+),
+vendor_products AS (             
+  SELECT v.vendor_name, p.product_name, lp.original_price
+  FROM latest_price lp
+  JOIN vendor  v USING (vendor_id)
+  JOIN product p USING (product_id)
+)
+SELECT
+  vp.vendor_name,
+  vp.product_name,
+  vp.original_price,
+  c.customers,
+  5 AS qty_per_customer,
+  c.customers * 5 * vp.original_price AS revenue
+FROM vendor_products vp
+CROSS JOIN cust c
+ORDER BY vp.vendor_name;
 
 
 -- INSERT
@@ -99,17 +197,34 @@ 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`. */
 
+CREATE TABLE product_units AS
+SELECT
+  p.*,
+  CURRENT_TIMESTAMP AS snapshot_timestamp
+FROM product p
+WHERE COALESCE(p.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
+SELECT
+  p.*,
+  CURRENT_TIMESTAMP AS snapshot_timestamp
+FROM product p
+WHERE p.product_name = 'Apple Pie';  
 
 
 -- 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');
 
 
 
@@ -130,6 +245,16 @@ 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 COLUMN current_quantity INT;
+
+UPDATE product_units AS pu
+SET current_quantity = COALESCE((
+  SELECT vi.quantity
+  FROM vendor_inventory vi
+  WHERE vi.product_id = pu.product_id
+  ORDER BY vi.market_date DESC, vi.vendor_id DESC 
+  LIMIT 1
+), 0)