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SQL assignment 2
neethil Dec 21, 2024
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SQL Assignment2
neethil Dec 21, 2024
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10 changes: 8 additions & 2 deletions 02_activities/assignments/Assignment2.md
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Expand Up @@ -45,18 +45,24 @@ There are several tools online you can use, I'd recommend [Draw.io](https://www.

**HINT:** You do not need to create any data for this prompt. This is a conceptual model only.

![alt text](sql_assign2part1_erd1.jpg)

#### Prompt 2
We want to create employee shifts, splitting up the day into morning and evening. Add this to the ERD.

![alt text](sql_assign2part1erd2.jpg)

#### 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...
```
Type 1 architecture stores the most updated address, that is, it will overwrite the previous address and retain only the newly updated address. One address is kept per customer overwriting any historical data.
Whereas, type 2 architecture retains history of all addresses entered by customer. Whenever the address updates,
it is stored as the active or current address, keeping a history of all previous addresses used by a customer along with the start and end dates of those addresses. The end date of a currrently active address is NULL.

```
***

## Section 2:
Expand Down
91 changes: 85 additions & 6 deletions 02_activities/assignments/assignment2.sql
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Expand Up @@ -20,6 +20,10 @@ 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(nullif(product_size,''),'')|| ' (' || coalesce(product_qty_type,'unit') || ')'
FROM product;



--Windowed Functions
Expand All @@ -32,18 +36,31 @@ 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 market_date, customer_id
,dense_rank() OVER(PARTITION BY customer_id ORDER BY market_date) AS md_count
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*
FROM
(
SELECT market_date, customer_id
,dense_rank() OVER(PARTITION BY customer_id ORDER BY market_date DESC) AS md_count
FROM customer_purchases
)x
WHERE x.md_count=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
,COUNT(*) OVER (PARTITION BY customer_id, product_id) AS product_count
FROM customer_purchases;

-- String manipulations
/* 1. Some product names in the product table have descriptions like "Jar" or "Organic".
Expand All @@ -57,11 +74,23 @@ 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, '-')+2))
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_size, product_name
,CASE WHEN instr(product_name, '-')>0 THEN
trim(substr(product_name, instr(product_name, '-')+2))
ELSE NULL
END AS description
FROM product
WHERE product_size REGEXP '\d';

-- UNION
/* 1. Using a UNION, write a query that displays the market dates with the highest and lowest total sales.
Expand All @@ -73,8 +102,29 @@ 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. */

DROP TABLE IF EXISTS total_sales_per_day;

CREATE TEMP TABLE total_sales_per_day AS

SELECT market_date, SUM(cost_to_customer_per_qty*quantity) as total_sales
FROM customer_purchases
GROUP BY market_date

SELECT*,'worst day' as daytype
FROM(
SELECT*, rank() OVER(ORDER BY total_sales) as rank_day
FROM total_sales_per_day
)x
WHERE rank_day=1

UNION

SELECT*,'best day' as daytype
FROM(
SELECT*, rank() OVER(ORDER BY total_sales DESC) as rank_day
FROM total_sales_per_day
)x
WHERE rank_day=1

/* SECTION 3 */

Expand All @@ -89,6 +139,19 @@ 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, (5*original_price*c.num_of_customer) as total_money
FROM vendor v
JOIN vendor_inventory vi
on v.vendor_id=vi.vendor_id
JOIN product p
on p.product_id=vi.product_id

CROSS JOIN
(
SELECT count(customer_id) AS num_of_customer
FROM customer
)c
GROUP BY vendor_name, product_name


-- INSERT
Expand All @@ -97,19 +160,25 @@ 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`. */


DROP TABLE IF EXISTS temp.product_units;
CREATE TEMP 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
VALUES (11,'White Bread', '1.5 lbs', 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.*/


DELETE FROM product_units
WHERE product_id = 11

-- UPDATE
/* 1.We want to add the current_quantity to the product_units table.
Expand All @@ -129,5 +198,15 @@ Finally, make sure you have a WHERE statement to update the right row,
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=coalesce(

(SELECT vi.quantity
FROM vendor_inventory vi
WHERE vi.product_id = product_units. product_id
ORDER BY vi.market_date DESC
LIMIT 1)
,0)
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