代写INFS2200/INFS7903 Assignment 1, 2024代写R编程

日期：2024-08-28 06:36

INFS2200/INFS7903 Assignment 1, 2024

Total Marks                 20 marks (20% of the course)

Due Date                     4:00 pm, 6th September 2024

What to submit           Report file and SQL script. file

Where to submit         Electronic submission via Blackboard

Assignment Version    1.1 (updated 7th August)

The goal of the project assignments is to gain practical experience in applying several database management concepts and techniques using the PostgreSQL DBMS. In particular, this assignment mainly focuses on improving database efficiency with views, indexing, and query planning.

Your main task is to first populate your database with appropriate data, then design, implement, and test the appropriate queries to perform. the tasks explained in the next sections.

You must work on this project individually. Academic integrity policies apply. Please refer to 3.60.04 Student Integrity and Misconduct of the University Policy for more information.

This document is in three sections: Section 1 describes the database schema for the assignment and provides instructions on downloading the script. file needed to create and populate the database. Section 2 describes the tasks to be completed for this assignment. The final section describes the submission guidelines and marking scheme.

Enjoy the project!

Section 1 - The LibraryDB Database

You are a developer working on LibraryDB.

The LibraryDB database records information about items in the library, its patrons and circulation of those items. It has four tables:

• Works - records metadata shared between each item such as title and author;

• Items - records each individual item (copy of a Work) available for loan;

• Patrons- records information about each patron of the library;

• Events - records loans, returns, holds and losses of Items by/to Patrons.

Entity-Relationship diagram

Setup

Before starting work on this assignment, please create a new database in psql, connect to it with the \c command, and run the setup file a1-2024-librarydb.sql with the \i command (it may take a minute). This ensures that your work on this assignment is separate from your other work.

The setup file is available from Blackboard and on Manta storage:

$ mget -O /infs2200/stor/data/assignments/1/a1-2024-librarydb.sql

Section 2 - Assignment 1 Tasks

Q1 CHECK Constraint (1 mark)

Most of the column-level constraints for the schema are simple NOT NULL, primary-key or foreign-key constraints which are best expressed as part of the table definition. However, sometimes it is useful to name a constraint, which means it can be defined separately to the table.

There are four permitted values of event_type: Loan, Return, Hold and Loss.

Write a constraint (named CK_EVENT_TYPE) to enforce this requirement.

Q2 Constraints with triggers

CHECK constraints should only be applied to data with immutable conditions. For example, it is bad practice to formulate a check based on the current time. Instead, triggers may be used.

Libraries have underage patrons, but these patrons may not have their own contact address and are likely not legally responsible for their losses. Rather, their guardian is.

Q2.1 (2 marks)

Write a trigger named BI_GUARDIAN and accompanying user-defined function named UDF_BI_GUARDIAN to ensure that all new patrons who are children (under 18 years old) have a guardian who is an existing patron.

Q2.2 (2 marks)

Write a trigger named BI_EMAIL_ADDR and accompanying user-defined function named UDF_BI_EMAIL_ADDR to ensure that all new patrons who are adults (18 years and older) have an email address.

Q3 Generating keys with sequences and triggers

A simple way to achieve a unique value is with an incrementing integer sequence. In modern PostgreSQL, where an integer column type is appropriate, this behaviour can be achieved by specifying the column type as serial rather than integer. This has been done for the Patrons and Events tables.

However, the primary key for the Items will also be printed as its barcode. The Library staff would like the initials of the library (UQ) to be at the start of the barcode, followed by a ten-digit number, followed by a one-digit checksum.

The checksum is the sum (mod 10) of the other digits.

Q3.1 Sequence creation (1 mark)

Create an integer sequence named ITEM_ID_SEQ for the Items table. The minimum value is 1000000000, the maximum is 9999999999 and the increment is 1.

Q3.2 Sequences and Triggers (2 marks)

Create a trigger named BI_ITEM_ID and accompanying user-defined function named UDF_BI_ITEM_ID to populate the primary keys for new Items as described above.

Q3.3 Sequence identification (1 mark)

Write a query to list the Postgres-internal sequence(s) created via the use of serial on the Patrons and Events tables.

Q4 Business logic with triggers

Q4.1 Losses (2 marks)

Sometimes an item is permanently lost by a patron. When this happens, they need to be charged the cost of its replacement, which is stored in the cost field of the relevant row in the Works table.

Write a trigger BI_LOSS_CHARGE and accompanying user-defined function UDF_BI_LOSS_CHARGE to populate the charge field when a new Loss is inserted into Events.

Q4.2 Missing Returns (4 marks)

Sometimes, an item may be improperly returned (such that the Return event is not recorded in the database) and then re-borrowed by another patron. In this case, the library system needs to credit the previous borrower with its return.

Write a trigger AI_MISSING_RETURN (and accompanying user-defined function UDF_AI_MISSING_RETURN) that detects this situation on a new Loan event and subsequently inserts a Return for the previous borrower, timestamped to one hour earlier.

(3 marks for correctly inserting returns across three different circulation-history scenarios; 1 mark for not inserting spurious returns.)

Q4.3 Holds (5 marks)

Patrons may request a hold on an item. For this event type, the time_stamp should represent the expiry of the hold, rather than the time the hold was initially placed.

A hold may only be placed on an item if it is available for lending AND not already held by any patron OR if it is currently on loan to a different patron. Otherwise, the hold must be rejected. (3 marks).

If a held item is currently on loan, the expiry of the hold is 42 days after its loan timestamp. Otherwise, the expiry of the hold is 14 days from the current time (2 marks).

Write a trigger BI_HOLDS (and accompanying user-defined function UDF_BI_HOLDS) to implement this functionality by rejecting the insert (if appropriate) or by setting the value of time_stamp.

Note: the current time for the purposes of this problem is given as the initial value of the time_stamp field. Do not use NOW() or similar. This is to allow for reliable testing.

Section 3 - Deliverables and Marking

There are 20 marks for functionality as listed in the task description.

Your assignment code will be tested with insertions and selections when relevant.

Triggers will be disabled when not being tested.

When your code must prevent an insertion, you should expect testing for false positives and false negatives.