Assignment two

02_activities/assignments/Assignment2.md

@@ -54,7 +54,10 @@ 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...
+type 1 = overwrite
+-- Updates the dimension record with the new value, overwriting the old value, does not save the old values
+type 2 = keep full history
+-- Inserts a new record for each change, preserving the old one. Full history retained
 ```
 
 ***

02_activities/assignments/assignment2.sql

@@ -7,8 +7,8 @@ We tell them, no problem! We can produce a list with all of the appropriate deta
 
 Using the following syntax you create our super cool and not at all needy manager a list:
 
-SELECT 
-product_name || ', ' || product_size|| ' (' || product_qty_type || ')'
+SELECT 
+product_name || ', ' || product_size|| ' (' || product_qty_type || ')'
 FROM product
 
 But wait! The product table has some bad data (a few NULL values). 
@@ -19,9 +19,23 @@ HINT: keep the syntax the same, but edited the correct components with the strin
 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 
+product_name || ', ' || product_size|| ' (' || product_qty_type || ')'
+FROM product;
+
+SELECT *
+FROM product
+WHERE product_size IS NULL
+   OR product_qty_type IS NULL
+   OR product_name is NULL;
+
+SELECT 
+    product_name || ', ' || 
+    COALESCE(product_size, '') || ' (' || 
+    COALESCE(product_qty_type, 'unit') || ')'
+FROM product;
+
 --Windowed Functions
 /* 1. Write a query that selects from the customer_purchases table and numbers each customer’s  
 visits to the farmer’s market (labeling each market date with a different number). 
@@ -32,18 +46,88 @@ 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 
+    customer_id,
+    market_date,
+    ROW_NUMBER() OVER (
+        PARTITION BY customer_id 
+        ORDER BY market_date)
+		AS visit_number
+FROM customer_purchases;
+
+SELECT 
+    customer_id,
+    market_date,
+    DENSE_RANK() OVER (
+        PARTITION BY customer_id 
+        ORDER BY market_date) 
+		AS visit_number
+FROM (SELECT DISTINCT customer_id, market_date
+    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 
+    customer_id,
+    market_date,
+    ROW_NUMBER() OVER (
+        PARTITION BY customer_id 
+        ORDER BY market_date DESC
+    ) AS visit_number
+FROM customer_purchases;
+
+SELECT 
+    customer_id,
+    market_date,
+    DENSE_RANK() OVER (
+        PARTITION BY customer_id 
+        ORDER BY market_date DESC
+    ) AS visit_number
+FROM (
+    SELECT DISTINCT customer_id, market_date
+    FROM customer_purchases
+);
+
+SELECT *
+FROM (
+    SELECT 
+        customer_id,
+        market_date,
+        ROW_NUMBER() OVER (
+            PARTITION BY customer_id 
+            ORDER BY market_date DESC
+        ) AS visit_number
+    FROM customer_purchases
+) AS ranked
+WHERE visit_number = 1;
+
+SELECT *
+FROM (
+    SELECT 
+        customer_id,
+        market_date,
+        DENSE_RANK() OVER (
+            PARTITION BY customer_id 
+            ORDER BY market_date DESC
+        ) AS visit_number
+    FROM (
+        SELECT DISTINCT customer_id, market_date
+        FROM customer_purchases
+    )
+) AS ranked
+WHERE visit_number = 1;
 
 /* 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 purchase_count
+FROM customer_purchases;
 
 -- String manipulations
 /* 1. Some product names in the product table have descriptions like "Jar" or "Organic". 
@@ -56,11 +140,33 @@ 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,
+    TRIM(
+        SUBSTR(
+            product_name,
+            INSTR(product_name, '-') + 1
+        )
+    ) AS description
+FROM product;
+
+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;
 
 
 /* 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
@@ -72,8 +178,21 @@ HINT: There are a possibly a few ways to do this query, but if you're struggling
 "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. */
-
-
+
+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
+)
+SELECT market_date, total_sales
+FROM sales_by_date
+WHERE total_sales = (SELECT MAX(total_sales) FROM sales_by_date)
+UNION
+SELECT market_date, total_sales
+FROM sales_by_date
+WHERE total_sales = (SELECT MIN(total_sales) FROM sales_by_date);
 
 
 /* SECTION 3 */
@@ -89,27 +208,57 @@ 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).  */
 
-
-
+SELECT
+    v.vendor_name,
+    p.product_name,
+    COUNT(c.customer_id) * 5 * vi.original_price AS total_revenue
+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 v.vendor_name, p.product_name;
+
 -- 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`. */
-
-
+
+CREATE TABLE product_units AS
+SELECT
+    p.*,                            
+    CURRENT_TIMESTAMP AS snapshot_timestamp 
+FROM product p
+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
+SELECT
+	product_id,
+	product_name,
+	product_size,
+	product_category_id,
+	product_qty_type,
+	CURRENT_TIMESTAMP as snapshot_timestamp
+FROM product
+WHERE 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 min(snapshot_timestamp)
+	FROM product_units
+	WHERE product_name = 'Apple Pie'
+);
 
 -- UPDATE
 /* 1.We want to add the current_quantity to the product_units table. 
@@ -128,6 +277,45 @@ 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;
+UPDATE product_units
+SET current_quantity = (
+    SELECT vi.quantity
+    FROM vendor_inventory vi
+    WHERE vi.product_id = product_units.product_id
+    ORDER BY vi.rowid DESC   
+    LIMIT 1
+);
+
+
+SELECT product_id, quantity
+FROM vendor_inventory vi
+WHERE rowid = (
+    SELECT MAX(rowid)
+    FROM vendor_inventory
+    WHERE product_id = vi.product_id
+);
+
+SELECT pu.product_id,
+       COALESCE((
+           SELECT vi.quantity
+           FROM vendor_inventory vi
+           WHERE vi.product_id = pu.product_id
+           ORDER BY vi.rowid DESC
+           LIMIT 1
+       ), 0) AS last_quantity
+FROM product_units pu;
+
+UPDATE product_units
+SET current_quantity = COALESCE((
+        SELECT vi.quantity
+        FROM vendor_inventory vi
+        WHERE vi.product_id = product_units.product_id
+        ORDER BY vi.rowid DESC
+        LIMIT 1
+    ), 0)
+WHERE product_id IN (
+    SELECT DISTINCT product_id
+    FROM vendor_inventory
+);