[tabassumaniqa]

What changes are you trying to make? (e.g. Adding or removing code, refactoring existing code, adding reports)

Adding assignment 2 responses and queries

What did you learn from the changes you have made?

More advanced SQL queries

Was there another approach you were thinking about making? If so, what approach(es) were you thinking of?

no

Were there any challenges? If so, what issue(s) did you face? How did you overcome it?

It was a lot to learn over a short period of time, I had to split the learning into smaller sessions and practice newly learned queries using the self assessments to ensure i retained the info

How were these changes tested?

Made sure all the queries run without errors on DB browser for SQLite

A reference to a related issue in your repository (if applicable)

n/a

Checklist

• I can confirm that my changes are working as intended

[github-actions]

SQL Assignment 2 feedback

SQL checks only. ERDs, written responses, and rubric point totals require instructor marking.

02_activities/assignments/DC_Cohort/assignment2.sql

Query 1: ✅ Correct

All product descriptions and NULL replacements are correct.

SQL and output

SELECT 
	product_name || ', ' || 
	COALESCE(product_size, '') || ' (' || 
	COALESCE(product_qty_type, 'unit') || ')'
FROM product;

[
  {
    "product_name || ', ' || \n\tCOALESCE(product_size, '') || ' (' || \n\tCOALESCE(product_qty_type, 'unit') || ')'": "Habanero Peppers - Organic, medium (lbs)"
  },
  {
    "product_name || ', ' || \n\tCOALESCE(product_size, '') || ' (' || \n\tCOALESCE(product_qty_type, 'unit') || ')'": "Jalapeno Peppers - Organic, small (lbs)"
  },
  {
    "product_name || ', ' || \n\tCOALESCE(product_size, '') || ' (' || \n\tCOALESCE(product_qty_type, 'unit') || ')'": "Poblano Peppers - Organic, large (unit)"
  }
]

Query 2: ✅ Correct

Visit dates are numbered correctly for each customer.

SQL and output

SELECT
	customer_id,
	market_date,
	DENSE_RANK() OVER (
		PARTITION BY customer_id
		ORDER BY market_date ASC
	) AS visit_number
FROM customer_purchases
WHERE market_date < '2022-04-29';

[
  {
    "customer_id": 1,
    "market_date": "2022-04-08",
    "visit_number": 1
  },
  {
    "customer_id": 1,
    "market_date": "2022-04-15",
    "visit_number": 2
  },
  {
    "customer_id": 1,
    "market_date": "2022-04-19",
    "visit_number": 3
  }
]

Query 3: ✅ Correct

Only each customer's most recent visit is returned.

SQL and output

SELECT *
FROM (
	SELECT DISTINCT
		customer_id,
		market_date,
		DENSE_RANK() OVER (
			PARTITION BY customer_id
			ORDER BY market_date DESC
		) AS visit_number
	FROM customer_purchases
)
WHERE visit_number = 1;

[
  {
    "customer_id": 1,
    "market_date": "2023-10-13",
    "visit_number": 1
  },
  {
    "customer_id": 2,
    "market_date": "2023-10-13",
    "visit_number": 1
  },
  {
    "customer_id": 3,
    "market_date": "2023-10-10",
    "visit_number": 1
  }
]

Query 4: ✅ Correct

The purchase count is correct for every customer and product.

SQL and output

SELECT *,
	COUNT(*) OVER (
		PARTITION BY customer_id, product_id
	) AS purchase_count
FROM customer_purchases
WHERE market_date < '2022-04-29';

[
  {
    "product_id": 4,
    "vendor_id": 7,
    "market_date": "2022-04-19",
    "customer_id": 1,
    "quantity": 5,
    "cost_per_quantity": 3.5,
    "transaction_time": "16:09:00",
    "purchase_count": 2
  },
  {
    "product_id": 4,
    "vendor_id": 7,
    "market_date": "2022-04-26",
    "customer_id": 1,
    "quantity": 3,
    "cost_per_quantity": 4,
    "transaction_time": "18:22:00",
    "purchase_count": 2
  },
  {
    "product_id": 5,
    "vendor_id": 8,
    "market_date": "2022-04-08",
    "customer_id": 1,
    "quantity": 1,
    "cost_per_quantity": 6.5,
    "transaction_time": "13:10:00",
    "purchase_count": 6
  }
]

Query 5: ✅ Correct

Product descriptions are extracted and trimmed correctly.

SQL and output

SELECT
	product_name,
	TRIM(
		SUBSTR(
			product_name,
			NULLIF(INSTR(product_name, '-'), 0) + 1
		)
	) AS description
FROM product;

[
  {
    "product_name": "Habanero Peppers - Organic",
    "description": "Organic"
  },
  {
    "product_name": "Jalapeno Peppers - Organic",
    "description": "Organic"
  },
  {
    "product_name": "Poblano Peppers - Organic",
    "description": "Organic"
  }
]

Query 6: ✅ Correct

Only product sizes containing a number are returned.

SQL and output

SELECT *
FROM product
WHERE product_size REGEXP '[0-9]';

[
  {
    "product_id": 4,
    "product_name": "Banana Peppers - Jar",
    "product_size": "8 oz",
    "product_category_id": 3,
    "product_qty_type": "unit"
  },
  {
    "product_id": 5,
    "product_name": "Whole Wheat Bread",
    "product_size": "1.5 lbs",
    "product_category_id": 3,
    "product_qty_type": "unit"
  },
  {
    "product_id": 7,
    "product_name": "Apple Pie",
    "product_size": "10\"",
    "product_category_id": 3,
    "product_qty_type": "unit"
  }
]

Query 7: ✅ Correct

The highest and lowest sales dates and totals are correct.

SQL and output

WITH day_sales AS (
	SELECT
		market_date,
		SUM(quantity * cost_per_quantity) 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_day,
		RANK() OVER (ORDER BY total_sales ASC) AS worst_day
	FROM day_sales
)

SELECT market_date, total_sales
FROM ranked_sales
WHERE best_day = 1

UNION

SELECT market_date, total_sales
FROM ranked_sales
WHERE worst_day = 1;

[
  {
    "market_date": "2022-12-20",
    "total_sales": 979
  },
  {
    "market_date": "2023-04-07",
    "total_sales": 272.5
  }
]

Query 8: ✅ Correct

Possible revenue is correct for every vendor and product.

SQL and output

SELECT
	v.vendor_name,
	p.product_name,
	COUNT(*) * 5 * vinv.original_price AS total_revenue
FROM (
	SELECT DISTINCT
		vendor_id,
		product_id,
		original_price
	FROM vendor_inventory
) AS vinv
INNER JOIN vendor as v
	ON vinv.vendor_id = v.vendor_id
INNER JOIN product AS p
	ON vinv.product_id = p.product_id
CROSS JOIN customer as c
GROUP BY
	v.vendor_id,
	p.product_id,
	vinv.original_price;

[
  {
    "vendor_name": "Fields of Corn",
    "product_name": "Sweet Corn",
    "total_revenue": 65
  },
  {
    "vendor_name": "Marco's Peppers",
    "product_name": "Habanero Peppers - Organic",
    "total_revenue": 908.7
  },
  {
    "vendor_name": "Marco's Peppers",
    "product_name": "Jalapeno Peppers - Organic",
    "total_revenue": 453.70000000000005
  }
]

Query 9: ✅ Correct

Unit products and current snapshot timestamps are correct.

SQL and output

CREATE TABLE product_units AS
SELECT
	*,
	CURRENT_TIMESTAMP AS snapshot_timestamp
FROM product
WHERE product_qty_type = 'unit';

/*
to check new table:

SELECT *
FROM product_units;
/*

Query 10: ✅ Correct

One product with a current timestamp was inserted.

SQL and output

INSERT INTO product_units
SELECT
	product.*,
	CURRENT_TIMESTAMP
FROM product
WHERE product_name = 'Apple Pie';

SELECT *
FROM product_units
WHERE product_name = 'Apple Pie';

[
  {
    "product_id": 7,
    "product_name": "Apple Pie",
    "product_size": "10\"",
    "product_category_id": 3,
    "product_qty_type": "unit",
    "snapshot_timestamp": "2026-11-09 01:14:00"
  },
  {
    "product_id": 7,
    "product_name": "Apple Pie",
    "product_size": "10\"",
    "product_category_id": 3,
    "product_qty_type": "unit",
    "snapshot_timestamp": "2026-11-09 01:14:01"
  }
]

Query 11: ✅ Correct

Only the older copy was removed; the inserted copy remains.

SQL and output

DELETE FROM product_units
WHERE product_name = 'Apple Pie'
AND snapshot_timestamp = (
	SELECT MIN(snapshot_timestamp)
	FROM product_units
	WHERE product_name = 'Apple Pie'
)
AND snapshot_timestamp < (
	SELECT MAX(snapshot_timestamp)
	FROM product_units
	WHERE product_name = 'Apple Pie'
);

Query 12: ✅ Correct

All rows remain and current_quantity matches the latest inventory.

SQL and output

ALTER TABLE product_units
ADD current_quantity INT;

UPDATE product_units
SET current_quantity = COALESCE((
	SELECT vinv.quantity
	FROM vendor_inventory AS vinv
	WHERE vinv.product_id = product_units.product_id
	ORDER BY vinv.market_date DESC
	LIMIT 1
), 0);

/*
-- check query

SELECT
    product_id,
    product_name,
    current_quantity
FROM product_units;
/*