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Create Pull request for homework2 of SQL by Tina Lin #2

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52 changes: 49 additions & 3 deletions 02_activities/homework/homework_2.sql
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Original file line number Diff line number Diff line change
@@ -1,42 +1,88 @@
--SELECT
/* 1. Write a query that returns everything in the customer table. */

Answer:
select * from customer

Another answer:
select customer_id, customer_first_name, customer_last_name, customer_postal_code from customer


/* 2. Write a query that displays all of the columns and 10 rows from the cus- tomer table,
sorted by customer_last_name, then customer_first_ name. */


Answer:
select * from customer
order by customer_last_name, customer_first_name
LIMIT 10


--WHERE
/* 1. Write a query that returns all customer purchases of product IDs 4 and 9. */
-- option 1
Answer:
select * from customer_purchases
where product_id = 4 or product_id = 9

-- option 2
Answer:
select * from customer_purchases
where product_id in (4, 9)

/*2. Write a query that returns all customer purchases and a new calculated column 'price' (quantity * cost_to_customer_per_qty),
filtered by vendor IDs between 8 and 10 (inclusive) using either:
1. two conditions using AND
2. one condition using BETWEEN
*/
-- option 1

Answer:
select *, quantity * cost_to_customer_per_qty as 'price' from customer_purchases
where vendor_id >= 8 AND vendor_id <= 10

-- option 2
Answer:
select *, quantity * cost_to_customer_per_qty as 'price' from customer_purchases
where vendor_id between 8 and 10

--CASE
/* 1. Products can be sold by the individual unit or by bulk measures like lbs. or oz.
Using the product table, write a query that outputs the product_id and product_name
columns and add a column called prod_qty_type_condensed that displays the word “unit”
if the product_qty_type is “unit,” and otherwise displays the word “bulk.” */

Answer:
select product_id, product_name,
CASE
WHEN product_qty_type = 'unit'
THEN 'unit'
ELSE 'bulk'
END as prod_qty_type_condensed
FROM product

/* 2. We want to flag all of the different types of pepper products that are sold at the market.
add a column to the previous query called pepper_flag that outputs a 1 if the product_name
contains the word “pepper” (regardless of capitalization), and otherwise outputs 0. */

Answer:
select product_id, product_name,
CASE
WHEN product_qty_type = 'unit'
THEN 'unit'
ELSE 'bulk'
END as prod_qty_type_condensed,
CASE
WHEN product_name like '%pepper%'
THEN 1
ELSE 0
END as pepper_flag
FROM product

--JOIN
/* 1. Write a query that INNER JOINs the vendor table to the vendor_booth_assignments table on the
vendor_id field they both have in common, and sorts the result by vendor_name, then market_date. */

Answer:
select * FROM vendor_booth_assignments as vba
INNER JOIN vendor as v
ON v.vendor_id = vba.vendor_id
ORDER BY v.vendor_name, vba.market_date