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Completed Assignment 2 #3

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156 changes: 11 additions & 145 deletions 02_activities/assignments/assignment2.sql
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Original file line number Diff line number Diff line change
Expand Up @@ -20,11 +20,7 @@ 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
COALESCE(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
Expand All @@ -36,53 +32,18 @@ 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;


/* 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 reverse_visit_number
FROM customer_purchases;


SELECT *
FROM (
SELECT
customer_id,
market_date,
ROW_NUMBER() OVER (
PARTITION BY customer_id
ORDER BY market_date DESC
) AS reverse_visit_number
FROM customer_purchases
) AS numbered_visits
WHERE reverse_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,
COUNT(*) OVER (
PARTITION BY customer_id, product_id
) AS customer_product_purchase_count
FROM customer_purchases;


-- String manipulations
/* 1. Some product names in the product table have descriptions like "Jar" or "Organic".
Expand All @@ -97,21 +58,10 @@ 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 *
FROM product
WHERE product_size REGEXP '[0-9]';


-- UNION
/* 1. Using a UNION, write a query that displays the market dates with the highest and lowest total sales.
Expand All @@ -123,41 +73,7 @@ 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. */

-- Step 1: Calculate total sales per market date
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
),

-- Step 2: Rank the market dates by total sales (descending and ascending)
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
)

-- Step 3: UNION results for best and worst days
SELECT
'Highest Sales Day' AS label,
market_date,
total_sales
FROM ranked_sales
WHERE best_rank = 1

UNION

SELECT
'Lowest Sales Day' AS label,
market_date,
total_sales
FROM ranked_sales
WHERE worst_rank = 1;


/* SECTION 3 */
Expand All @@ -172,64 +88,28 @@ 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). */
SELECT
v.vendor_name,
p.product_name,
SUM(5 * vi.cost_to_customer_per_qty) 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 (
SELECT DISTINCT customer_id FROM customer
) AS customers
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
*,
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_qty_type,
product_category_id,
snapshot_timestamp
)
VALUES (
24, -- Use a unique ID not in use
'Pumpkin Pie',
'1 each',
'unit',
3, -- Replace with a valid category ID as appropriate
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_id = 7
AND snapshot_timestamp < (
SELECT MAX(snapshot_timestamp)
FROM product_units
WHERE product_id = 7
);


-- UPDATE
/* 1.We want to add the current_quantity to the product_units table.
Expand All @@ -248,20 +128,6 @@ 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 pu
SET current_quantity = COALESCE((
SELECT vi.quantity
FROM vendor_inventory vi
WHERE vi.product_id = pu.product_id
AND vi.market_date = (
SELECT MAX(market_date)
FROM vendor_inventory
WHERE product_id = pu.product_id
)
LIMIT 1
), 0);