Assignment 2

02_activities/assignments/Assignment2.md

@@ -44,17 +44,29 @@ Additionally, include a date table.
 There are several tools online you can use, I'd recommend [Draw.io](https://www.drawio.com/) or [LucidChart](https://www.lucidchart.com/pages/).
 
 **HINT:** You do not need to create any data for this prompt. This is a conceptual model only. 
+# This is the pdf for this prompt:
+[text](Bookstore1.drawio.pdf)
 
 #### Prompt 2
 We want to create employee shifts, splitting up the day into morning and evening. Add this to the ERD.
+# This is the pdf for this prompt:
+[text](Bookstore2.drawio.pdf)
 
 #### 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? 
 
 **HINT:** search type 1 vs type 2 slowly changing dimensions. 
 
 ```
-Your answer...
+The two different types of architectures related to the concept of Slowly Changing Dimensions (SCD) can be used to store a CUSTOMER_ADDRESS table are:
+
+Overwrite (Type 1 SCD): simply overwrites an existing record with the new data. 
+Only the latest address is stored. This is simple to implement and maintain, and requires less storage space as no historical data is kept. That no historical data is kept is also the downside since the system can't track changes over time.
+
+Add New Row (Type 2 SCD): a new row is added for each change, while the old one is retained, which allows you to maintain a complete history of address changes for each customer. If knowing about address changes is important then this is obviously useful; however, it is more complex and does require more storage space.
+
+
+
 ```
 
 ***

02_activities/assignments/assignment2.sql

@@ -19,7 +19,11 @@ 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 || ', ' || 
+	COALESCE(product_size, '') || ' (' || 
+	COALESCE(product_qty_type, 'unit') || ')'
+FROM product;
 
 
 --Windowed Functions
@@ -32,17 +36,63 @@ 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(). */
 
+--Using Row_number:
+SELECT
+    customer_id,
+    market_date,
+    product_id,
+    quantity,
+    cost_to_customer_per_qty,
+    ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY market_date) AS visit_number
+FROM customer_purchases;
+
+--Using Dense_rank:	
+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) AS unique_visits;
 
 
 /* 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. */
-
+--Reverse the numbering
+SELECT
+    customer_id,
+    market_date,
+    ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY market_date DESC) AS visit_number
+FROM customer_purchases;
+
+--Using a sub-query:
+SELECT 
+    customer_id,
+    market_date,
+    visit_number
+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 subquery
+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
+    customer_id,
+    product_id,
+    market_date,
+    quantity,
+    cost_to_customer_per_qty,
+    COUNT(*) OVER (PARTITION BY customer_id, product_id) AS purchase_count
+FROM customer_purchases;
 
 
 -- String manipulations
@@ -57,10 +107,23 @@ 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. */
 
+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
+    product_name,
+    product_size
+FROM product
+WHERE product_size REGEXP '[0-9]';
 
 
 -- UNION
@@ -73,7 +136,34 @@ 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 SalesPerDate AS (
+    SELECT
+        market_date,
+        SUM(quantity * cost_to_customer_per_qty) AS total_sales
+    FROM customer_purchases
+    GROUP BY market_date
+),
+RankedSales AS (
+    SELECT
+        market_date,
+        total_sales,
+        RANK() OVER (ORDER BY total_sales DESC) AS rank_desc,
+        RANK() OVER (ORDER BY total_sales ASC) AS rank_asc
+    FROM SalesPerDate
+)
+SELECT
+    market_date,
+    total_sales,
+    'Best Day' AS sales_category
+FROM RankedSales
+WHERE rank_desc = 1
+UNION
+SELECT
+    market_date,
+    total_sales,
+    'Worst Day' AS sales_category
+FROM RankedSales
+WHERE rank_asc = 1;
 
 
 /* SECTION 3 */
@@ -89,26 +179,94 @@ 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).  */
 
-
-
+WITH VendorProduct AS (
+    SELECT 
+        v.vendor_name,
+        p.product_name,
+        vi.original_price AS price
+    FROM 
+        vendor_inventory vi
+    JOIN 
+        vendor v ON vi.vendor_id = v.vendor_id
+    JOIN 
+        product p ON vi.product_id = p.product_id
+), 
+CustomerCount AS (
+    SELECT 
+        COUNT(*) AS customer_count
+    FROM 
+        customer
+)
+SELECT 
+    vp.vendor_name,
+    vp.product_name,
+    SUM(5 * vp.price * cc.customer_count) AS total_revenue
+FROM 
+    VendorProduct vp,
+    CustomerCount cc
+GROUP BY 
+    vp.vendor_name, vp.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 
+    *,
+    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 (
+    product_id,
+    product_name,
+    product_size,
+    product_category_id,
+    product_qty_type,
+    snapshot_timestamp
+)
+VALUES (
+    1001, 
+    '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.*/
+--Identify the product_id of the older record:
 
+SELECT 
+    product_id,
+    product_name,
+    snapshot_timestamp
+FROM 
+    product_units
+WHERE 
+    product_name = 'Apple Pie'
+ORDER BY 
+    snapshot_timestamp ASC;
+
+--Delete older record:
+DELETE FROM 
+    product_units
+WHERE 
+    product_id = 1001;
 
 
 -- UPDATE
@@ -128,6 +286,30 @@ 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. */
 
+-- 1: Add the column
+ALTER TABLE product_units
+ADD current_quantity INT;
+
+-- 2: Get the last quantity per product using ROW_NUMBER()
+WITH LastQuantity AS (
+    SELECT 
+        vi.product_id,
+        COALESCE(vi.quantity, 0) AS last_quantity,
+        ROW_NUMBER() OVER (PARTITION BY vi.product_id ORDER BY vi.market_date DESC) AS row_num
+    FROM 
+        vendor_inventory vi
+)
+-- 3: Update the current_quantity in product_units
+UPDATE product_units
+SET current_quantity = (
+    SELECT 
+        lq.last_quantity 
+    FROM 
+        LastQuantity lq
+    WHERE 
+        lq.product_id = product_units.product_id
+        AND lq.row_num = 1
+);
 
 
 

04_this_cohort/live_code/module_4/FULL_OUTER_JOIN_UNION.sql

@@ -0,0 +1,47 @@
+--FULL OUTER JOIN with a UNION
+
+DROP TABLE IF EXISTS temp.store1; 
+CREATE TEMP TABLE IF NOT EXISTS temp.store1
+(
+costume TEXT,
+quantity INT
+);
+
+INSERT INTO temp.store1
+VALUES("tiger",6),
+        ("elephant",2),
+        ("princess", 4);
+
+
+DROP TABLE IF EXISTS temp.store2;
+CREATE TEMP TABLE IF NOT EXISTS temp.store2
+(
+costume TEXT,
+quantity INT
+);
+
+INSERT INTO temp.store2
+VALUES("tiger",2),
+	("dancer",7),
+	("superhero", 5);
+
+SELECT 
+s1.costume
+,s1.quantity as store1_quantity
+,s2.quantity as store2_quantity
+
+FROM store1 s1
+LEFT JOIN store2 s2
+	ON s1.costume = s2.costume
+
+UNION ALL
+
+SELECT
+s2.costume
+,s1.quantity
+,s2.quantity 
+
+FROM store2 s2
+LEFT JOIN store1 s1
+	ON s1.costume = s2.costume
+WHERE s1.costume IS NULL

04_this_cohort/live_code/module_4/IFNULL_NULLIF.sql

@@ -0,0 +1,23 @@
+--IFNULL and coalesce + NULLIF
+
+SELECT *
+,IFNULL(product_size, 'Unknown')  as new_product_size
+
+--less meaningful "conceptual"
+,IFNULL(product_size, product_qty_type) -- both null, results with null
+,coalesce(product_size,product_qty_type,'missing') -- if first the value is null, the second is null, then do the third value
+,IFNULL(IFNULL(product_size, product_qty_type),'missing') -- same but have to wrap within
+
+
+FROM product;
+
+SELECT *
+,IFNULL(product_size, 'Unknown')  as new_product_size
+,NULLIF(product_size, '') -- finding the values that product_size column is "blank" and setting them to null
+,coalesce(NULLIF(product_size, ''),  'unknown') as good_product_size
+,IFNULL(NULLIF(product_size, ''),  'unknown') as good_product_size
+
+FROM product
+
+WHERE NULLIF(product_size, '') IS NULL -- both blanks and NULLs
+--WHERE product_size IS NULL -- only NULLs