Final Assignment 2 submission - SQL included

02_activities/assignments/Microcredential_Cohort/Assignment2.md

@@ -56,7 +56,50 @@ 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...
+#### Prompt 3
+The store wants to keep customer addresses. Propose two architectures for the CUSTOMER_ADDRESS table, one that will retain changes, and another that will overwrite. Which is type 1, which is type 2?
+
+**Answer:**
+
+### Architecture 1: Overwrite Existing Address (Type 1 Slowly Changing Dimension)
+In this model, the CUSTOMER_ADDRESS table stores only the customer’s current address.
+
+Suggested columns:
+- customer_address_id
+- customer_id
+- street_address
+- city
+- province
+- postal_code
+- country
+
+When a customer updates their address, the existing record is updated using an UPDATE statement. The previous address is overwritten and not retained.
+
+This is a **Type 1 Slowly Changing Dimension** because historical address data is not preserved.
+
+
+### Architecture 2: Retain Address History (Type 2 Slowly Changing Dimension)
+In this model, the CUSTOMER_ADDRESS table stores both current and historical addresses.
+
+Suggested columns:
+- customer_address_id
+- customer_id
+- street_address
+- city
+- province
+- postal_code
+- country
+- effective_start_date
+- effective_end_date
+- is_current
+
+When a customer changes address:
+1. The previous record is marked with an effective_end_date.
+2. A new row is inserted with the updated address and marked as current.
+
+This preserves address history over time.
+
+This is a **Type 2 Slowly Changing Dimension** because historical changes are retained.
 ```
 
 ***

02_activities/assignments/Microcredential_Cohort/assignment2.sql

@@ -23,8 +23,11 @@ Edit the appropriate columns -- you're making two edits -- and the NULL rows wil
 All the other rows will remain the same. */
 --QUERY 1
 
-
-
+SELECT
+product_name || ', ' ||
+coalesce(product_size, '') || '  ('||
+coalesce (product_qty_type, 'unit') ||  ')'
+FROM product;
 
 --END QUERY
 
@@ -41,8 +44,15 @@ HINT: One of these approaches uses ROW_NUMBER() and one uses DENSE_RANK().
 Filter the visits to dates before April 29, 2022. */
 --QUERY 2
 
-
-
+SELECT 
+customer_id,
+market_date,
+dense_rank() OVER (
+	PARTITION by customer_id
+	ORDER  by market_date
+) as visit_number
+FROM  customer_purchases
+WHERE market_date < '2022-04-29';
 
 --END QUERY
 
@@ -53,8 +63,21 @@ only the customer’s most recent visit.
 HINT: Do not use the previous visit dates filter. */
 --QUERY 3
 
-
-
+WITH ranked_visits AS (
+    SELECT
+        customer_id,
+        market_date,
+        ROW_NUMBER() OVER (
+            PARTITION BY customer_id
+            ORDER BY market_date DESC
+        ) AS recent_visit_rank
+    FROM customer_purchases
+)
+
+SELECT *
+FROM ranked_visits
+WHERE recent_visit_rank = 1;
+
 
 --END QUERY
 
@@ -66,9 +89,16 @@ You can make this a running count by including an ORDER BY within the PARTITION
 Filter the visits to dates before April 29, 2022. */
 --QUERY 4
 
-
-
-
+SELECT
+customer_id,
+product_id,
+market_date,
+count(*) OVER (
+	PARTITION by customer_id, product_id
+	) as purchase_count
+	FROM  customer_purchases
+	WHERE market_date < '2022-04-29';
+
 --END QUERY
 
 
@@ -85,7 +115,14 @@ Remove any trailing or leading whitespaces. Don't just use a case statement for
 Hint: you might need to use INSTR(product_name,'-') to find the hyphens. INSTR will help split the column. */
 --QUERY 5
 
-
+SELECT
+product_name,
+CASE
+    WHEN INSTR(product_name, '-') > 0 THEN
+        TRIM(SUBSTR(product_name, INSTR(product_name, '-') + 1))
+    ELSE NULL
+END AS description
+FROM product;	
 
 
 --END QUERY
@@ -94,23 +131,50 @@ 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. */
 --QUERY 6
 
-
-
+SELECT  *
+FROM product
+WHERE product_size REGEXP  '[0-9]';
 
 --END QUERY
 
 
 -- UNION
-/* 1. Using a UNION, write a query that displays the market dates with the highest and lowest total sales.
-
-HINT: There are a possibly a few ways to do this query, but if you're struggling, try the following: 
-1) Create a CTE/Temp Table to find sales values grouped dates; 
-2) Create another CTE/Temp table with a rank windowed function on the previous query to create 
-"best day" and "worst day"; 
-3) Query the second temp table twice, once for the best day, once for the worst day, 
-with a UNION binding them. */
+/* 1. Using a UNION, write a query that displays the market dates with the highest
+and lowest total sales.
+
+HINT:
+1) Create a CTE/Temp Table to find sales values grouped by dates
+2) Create another CTE/Temp table with a rank windowed function
+3) Query the second temp table twice, once for the best day and once for the worst day,
+then bind them with UNION.
+*/
 --QUERY 7
 
+WITH sales_by_date AS (
+    SELECT
+        market_date,
+        SUM(quantity * cost_to_customer_per_qty) AS total_sales
+    FROM customer_purchases
+    GROUP  BY market_date
+),
+ranked_sales AS (
+    SELECT
+        market_date,
+        total_sales,
+        RANK() OVER (ORDER BY total_sales DESC) AS best_rank,
+        RANK() OVER (ORDER BY total_sales ASC) AS worst_rank
+    FROM sales_by_date
+)
+
+SELECT market_date, total_sales
+FROM ranked_sales
+WHERE best_rank = 1
+
+UNION
+
+SELECT market_date, total_sales
+FROM ranked_sales
+WHERE worst_rank = 1;
 
 
 
@@ -132,9 +196,29 @@ How many customers are there (y).
 Before your final group by you should have the product of those two queries (x*y).  */
 --QUERY 8
 
-
-
-
+SELECT
+    vendor_name,
+    product_name,
+    COUNT(customer_id) * 5 * cost_to_customer_per_qty AS total_revenue
+FROM (
+    SELECT
+        vi.vendor_id,
+        v.vendor_name,
+        p.product_name,
+        vi.cost_to_customer_per_qty,
+        c.customer_id
+    FROM vendor_inventory vi
+    JOIN vendor v
+        ON vi.vendor_id = v.vendor_id
+    JOIN product p
+        ON vi.product_id = p.product_id
+    CROSS JOIN customer c
+)
+GROUP BY
+    vendor_name,
+    product_name,
+    cost_to_customer_per_qty;
+
 --END QUERY
 
 
@@ -145,7 +229,12 @@ It should use all of the columns from the product table, as well as a new column
 Name the timestamp column `snapshot_timestamp`. */
 --QUERY 9
 
-
+CREATE TABLE product_units AS
+SELECT
+    *,
+    CURRENT_TIMESTAMP AS snapshot_timestamp
+FROM product
+WHERE product_qty_type = 'unit';	
 
 
 --END QUERY
@@ -155,7 +244,13 @@ Name the timestamp column `snapshot_timestamp`. */
 This can be any product you desire (e.g. add another record for Apple Pie). */
 --QUERY 10
 
-
+INSERT INTO product_units
+SELECT
+    *,
+    CURRENT_TIMESTAMP
+FROM product
+WHERE product_name = 'Apple Pie'
+LIMIT 1;
 
 
 --END QUERY
@@ -167,34 +262,52 @@ This can be any product you desire (e.g. add another record for Apple Pie). */
 HINT: If you don't specify a WHERE clause, you are going to have a bad time.*/
 --QUERY 11
 
+DELETE FROM product_units
+WHERE product_name = 'Apple Pie'
+AND snapshot_timestamp = (
+    SELECT MIN(snapshot_timestamp)
+    FROM product_units
+    WHERE product_name = 'Apple Pie'
+);
 
 
 
 --END QUERY
 
 
 -- 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.
+/* 1. We want to add the current_quantity to the product_units table.
 
+First, add a new column:
 ALTER TABLE product_units
-ADD current_quantity INT;
+ADD COLUMN current_quantity INT;
 
-Then, using UPDATE, change the current_quantity equal to the last quantity value from the vendor_inventory details.
-
-HINT: This one is pretty hard. 
-First, determine how to get the "last" quantity per product. 
-Second, coalesce null values to 0 (if you don't have null values, figure out how to rearrange your query so you do.) 
-Third, SET current_quantity = (...your select statement...), remembering that WHERE can only accommodate one column. 
-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. */
---QUERY 12
+Then using UPDATE, change current_quantity equal to the last quantity
+value from vendor_inventory.
 
+HINT:
+- determine last quantity per product
+- coalesce null values to 0
+- use product_units.product_id in WHERE
+*/
 
+--QUERY 12
 
+ALTER TABLE product_units
+ADD  COLUMN current_quantity INT;
+
+UPDATE  product_units
+SET current_quantity = COALESCE(
+    (
+        SELECT quantity
+        FROM vendor_inventory vi
+        WHERE vi.product_id = product_units.product_id
+        ORDER BY market_date DESC
+        LIMIT 1
+    ),
+    0
+);
 
 --END QUERY
 
 
-