Assignment 5 A5: Imperative SQL


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Assignment 5
A5: Imperative SQL
The goal of this assignment is to write functions and triggers that add functionality to our database.
What to turn in
You must turn in a .sql file on Canvas. Basically, we want to be able to hit
execute and run your sql code to create your imperative SQL and run it.
This means that any comments or text answers in your file should be in SQL
What’s In and Out of Scope
This is intended to be an imperative SQL assignment. Therefore, you must
write code, although you may need to embed declarative SQL in some of
your code. You may use VIEWs as needed and you may use standard builtin Postgres functions (e.g. ROUND, IF or CASE statements). If you’re not
sure if something is allowed, ask!

Ground Rules
1. Use the function and trigger names specified
2. Load data as provided
Loading the data
The file name A5tableDefns.sql contains all of the table creation statements. Run this file to create the tables.
Note that in these definitions we have added an attribute to sale: partOfSale.
This attribute is usually NULL, but will be populated if someone purchases
an add on product. For example, if someone buys a kid cone with an extra
topping, the record for the extra topping will include the saleId of that kid
The data are in A5data.sql, sale20181104.sql, and saleDetail20181104.sql
1 Functions
1. (10 points) Write a function, numProductsAtEvent, that returns the
total number of products sold during an event. NumProductsAtEvent
should take as an argument an eventId. If there is no event with the
specified eventId, return -1.
Execute the following statement and include the result in the comments
in your homework submission.
SELECT numProductsAtEvent(3);
2. (15 points) Write a function, fractionXtra, that computes the number
of ‘extra’ toppings or flavors that were sold per eligible base product at
each event. For example, cups of ice cream can have extra toppings.
The table xtra has been provided to help you determine which ‘extra’
(or ‘add-on’) productCodes go with which base products. For example,
all of the ‘sundae’ base products can have an ‘sx’ extra topping product.
In this function you want to tally how many products were sold that
COULD have an extra topping or flavor and determine what fraction of
the those products actually DID have an extra topping or product sold.
FractionXtra should take an eventId as an argument and return a
decimal, with 3 decimal places, indicating the fraction of extra items
sold. If the specified event does not exist, return -1.
For example, if we have the following sales:
eventId saleId productCode
101 1334 c1
101 1335 cx
101 1336 d1
101 1337 dx
101 1339 wc
c1, d1, and wc all could have extra toppings. 2/3 of them do.
SELECT fractionXtra(101); would return 0.667.
Execute the following statements and include the results in the comments in your homework submission.
SELECT fractionXtra(4);
SELECT fractionXtra(32);
3. (50 points) We want to know how well the power of suggestion works.
If one person in line orders a particular product, are the next people
in line likely to order that same type of product or not? To determine
this, we want to look at sequential product purchases.
Since product sales are entered into the sale table in the order in which
they were purchased, we have an ordering for the products at each event.
Rather than comparing all possible combinations of the 27 products, we
group similar products into product types. The table ProductType has
been provided that maps each productCode to one of 9 product types.
Your function should populate the table productTypePairs with the
counts of products, by type, that follow each other.
For example: If we sell a milkshake, then a pint of ice cream, then the
value of ‘ice cream beverage’–’pint’ should be incremented by one. If
we sell a pint of ice cream, and then a milkshake, the value of ‘pint’–
‘ice cream beverage’ should be incremented by one. Note that since we
care about order, these two pairs are not equivalent. Note that your
table should contain ‘typeX’–’typeX’ pairs as well. For example ‘cone’-
‘Extra’ products are special, since they are add-ons. To handle these,
we skip any ‘extra’ products in our regular counts and then we handle
them all by themselves. We only want to know about ‘extra’–’extra’
orderings. In this case we don’t care what the base product was – we
just want to know that if one person in line orders an extra ‘something,’
did the next person order something ‘extra’ as well? So, we want to
count extra–extra pairs. At the product code level, ‘slx’– ‘wx’ would
increment our count, as would ‘cx’ – ‘dx’. Create a single record in
productTypePairs with productType1 = ‘extra’ and productType2 =
‘extra’ to store this count. Increment this count when you see an ‘extra’–
‘extra’ sequence or when there is at most one non-extra product between
the two extra purchases.
For example, if we have the following sales:
eventId saleId productCode
42 1334 c1
42 1335 cx
42 1336 d1
42 1337 dx
42 1338 wx
42 1339 wc
This would count two ‘extra’–’extra’ pairs: one for cx and dx and one
for dx and wx.
Chains should not cross event boundaries. In other words, the last
product purchased at one event should not be paired with the first
product purchased at the next event.
Write the function productChains that implements the logic described
2 Triggers
1. (10 points) Recall, that some of our maintenance items need to occur
after certain ‘triggers.’ For example, the ice cream machines must be
cleaned after each event and the generator should be refueled after 40
hours of use.
Create a trigger named printMaintAlert that fires after inserts to the
truckEvent table. This trigger should print the following message:
New event on <new date time. Don’t forget to get clean water!
Where <new date time should be the eventStart timestamp for the
new event. The event should be allowed to be inserted.
Run the following code to test your trigger. Include the results in a
comment in your submission.
INSERT INTO truckEvent(eventName, eventStart, plannedEnd)
(‘COMP430/530 party’, ‘2018-11-30 2:00 PM’, ‘2018-11-30 2:50 PM’);
In order to insert this record into the truckEvent table, you are likely
going to need to reset the sequence object that assigns new SERIAL
ids to the eventId attribute in truckEvent. You can use the ALTER
SEQUENCE command to set the new value of the attribute to 1 past the
maximum id value in the truckEvent table. You can look up the highest
eventId value manually and execute this statement. It will only need to
be run once. After that, the eventId should handle new inserts without
2. (15 points) Event Booking Trigger We don’t want to accidentally over
book events.
Add an attribute named validEvent to the truckEvent table, with a
default value of 0. If this field is set to 1, the event is valid. If it is 0,
the event is not valid and the owner has to decide what to do.
Set the value of this field to 1 for all existing records in the table. Provide
the SQL statement to do this!
Next, add an insert trigger(s) to the truckEvent table that will insert the
new record, but set the valid value to 0 if the new truckEvent overlaps
with any existing event and will print the following error message:
New event <eventName on <new date time overlaps with the following scheduled events:
and then lists the conflicts in order by eventStart.
If the new event does NOT overlap with any other event, set the valid
flag to 1.
Finally, run the following query and include the results in your write-up:
INSERT INTO truckEvent(eventName, eventStart, plannedEnd)
(‘Event1’, ‘2017-06-16 14:30’, ‘2017-06-16 20:45’),
(‘Event2’, ‘2017-09-07 15:30’, ‘2017-09-07 18:00’),
(‘Event3’, ‘2017-09-07 17:30’, ‘2017-09-07 21:00’);
FROM truckEvent
WHERE eventName in( ‘Event1’, ‘Event2’, ‘Event3’)
ORDER BY eventName;

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