Practical 2: Database management with SQLite Solved

In this assignment, you are asked to convert an E–R model into an SQLite database, populate it with test data, and then run a number of SQL queries.

You are expected to have read and understood all the information in this specification at least a week before the deadline. You must contact the lecturer regarding any queries well in advance of the deadline.


Summary

In lectures and exercise classes, we have spent a fair amount of time on SQL, and its use in database creation, data insertion, and database querying. This assignment will help you to develop and practise skills in all of these areas:

    • converting E–R data models into SQL;

    • understanding the relationship between conceptual and logical data models;

    • enforcing database integrity;

    • confidently translating business queries to and from SQL.

This is an individual assignment. You are expected to work on your own to complete the tasks in this assignment.

E–R Model

We will work with the E–R Model for a bookstore scenario, where an online bookstore uses a database to manage details about books, customers, suppliers, and book orders.

Books are offered in various types (paperback, hardcover, audiobook). A book can be available in more than one edition, identified by the edition’s number. A book has a comma separated list of authors, stored in the attribute author. Each book may be available from various suppliers at a different supply price. The customers are able to rate books and assign to them a rating from 1 to 5 stars. Customers are able to place orders, which may include many different books, as well as multiple copies of a particular book.

The rest of the details must be inferred from the E–R diagram on Figure 1. In case of any ambiguities or unspecified details in the scenario above, your implementation should always match the model described by this E–R diagram.






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Figure 1: E–R Diagram for a bus company scenario

Notation:

    • Primary key  —  underlined

    • Discriminator  —  underlined with dashes

    • Defining relationship  —  doubled diamond

    • Cardinality of one  —  arrow

    • Total participation  —  doubled line

    • Multivalued attributes  —  in curly braces

    • Relationship attributes  —  connected to the relation with a dashed line

Notes:

    • in the Book relation, if a book has more than one author, their names are stored in the attribute author, separated by commas.

    • in the Edition relation, admissible values of the attribute edition are positive integers, and admissible values of the attribute type are audiobook, hardcover, and paperback.

    • in the Reviews relationship, admissible values of the attribute Rating are 1, 2, 3, 4, 5.

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Tasks

Task 1: Translation

Translate the E–R model into the corresponding database schema, i.e. into the collection of relation schemas. In your report, present the relation schemas and provide a brief rationale for any design choices you make. Be sure to identify appropriate primary keys, foreign keys, and attribute types.

Task 2: SQL Data Definition

Using the Command Line Shell for SQLite (https://sqlite.org/cli.html) or DBeaver (https:

//dbeaver.io/), create an SQLite database, which corresponds to the database schema from Task 1.

To complete this task, you should create a plain text file called bookstore.sql, containing SQL code to define tables for each relational schema from Task 1, and then insert data into your tables.

You need to create about 10 rows per each table, and make sure that you insert rows which make each query from Task 3 to return at least 2 results (you may revisit this task later, and add extra data while working on Task 3, if necessary).

Make sure that integrity constraints are enforced. In SQLite, you have to put the line

PRAGMA foreign_keys = TRUE;

in the the file bookstore.sql in the beginning of the script, above the commands used to create and populate the tables. In addition to specifying primary and foreign keys, and attribute types, you are encouraged to use additional SQL features to enforce database integrity, e.g. cascading actions, default values, etc.

Populating the database with the test data, you may find it useful to invest some efforts into making the values of attributes minimally meaningful and recognisable. This will help you to check that the queries developed in Task 3 are returning correct results.

You have to ensure that the bookstore.sql script is runnable in a clean new session in the Com-mand Line Shell for SQLite or in DBeaver, and, starting from an empty database, will create tables and populate them with data, without any error messages.

In your report, give the high-level overview of this process, describing your approach to developing and testing the SQL code to ensure the integrity of your data. If necessary, you may include fragments of the code from bookstore.sql to illustrate your statements (but you do not have to repeat the whole content of bookstore.sql, since this file will be submitted separately).

Task 3: SQL Data Manipulation

Extend the bookstore.sql script created in Task 2, adding to it (below the statements to create table and insert date), SQL code to perform the following queries:

    1. List all books published by “Ultimate Books” which are in the “Science Fiction” genre;

    2. List titles and ratings of all books in the “Science and Technology” genre, ordered first by rating (top rated first), and then by the title;

    3. List all orders placed by customers with customer address in the city of Edinburgh, since 2020, in chronological order, latest first;

    4. List all book editions which have less than 5 items in stock, together with the name, account number and supply price of the minimum priced supplier for that edition.

    5. Calculate the total value of all audiobook sales since 2020 for each publisher;

Furthermore, formulate at least 3 new queries, stating them as precisely as you can in plain English.

Implement them in SQL, and include the SQL code for all the queries, and their output, in the report.

Finally, create at least two appropriate views, stating what the view represents (in plain English), and including the SQL code used to create the views, and their output, in the report.


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Writing SQL code, you should adhere to some consistent coding style (for example, to the “SQL Style Guide” by Simon Holywell, https://www.sqlstyle.guide/ or any other consistent convention), and use sensible names of attributes, capitalisation, indentation, blank lines and comments to make your code readable and understandable.

Include all descriptions in plain English, corresponding SQL commands and their outputs in the report, either as copied and pasted text (recommended), or as screenshots.

When including SQL code and input/output from the Command Line Shell for SQLite, pay atten-tion to its formatting - in particular, use monospace font to preserve code indentation and tables layout. It is acceptable to use screenshots instead, provided that they are of high quality. To improve screen-shots readability, you can resize windows, change font size, and change settings to use dark text on a light background; note however that screenshots with SQL code are not useful since the text on them can not be searched and copied.

Task 4: Reflection

Describe briefly your experience of the process of converting the E–R model into SQL and working with data, linking back to the work done in Tasks 1–3. What did you feel you did well? What did you find challenging? What problems did you encounter, if any, and how did you try to resolve those? What would you do differently, if anything? This should be a short reflective section of your report. You can say as much or as little as you want, but as guidance, between half a page to a page should be enough.

Submission

Prepare a zip archive, containing two files:

    • the report in PDF format, with sections per task as above;

    • the bookstore.sql script in plain text format.

If you have correctly followed the requirements of Tasks 2 and 3, the bookstore.sql should con-tain complete SQL code needed to reproduce your work. It is recommended to check before submission that your code works without errors on school systems by running it in the terminal with

sqlite3 --init bookstore.sql

Submit the archive as specified above via MMS by the deadline, checking to make sure that the version you submit is the one you mean to submit.


Marking

The basic requirements for this practical are:

    • A correct translation of the given E–R model into corresponding relational schema, together with primary and foreign keys;

    • Correct SQL implementing the schema (should work in SQLite);

    • SQL corresponding to the given queries, and to the self-defined queries (should work in SQLite);

    • Correct and appropriate view definitions (should work in SQLite);

    • Runnable without error messages, properly formatted and appropriately commented SQL code in the bookstore.sql script.






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A competent work addressing all these requirements will get marks up to 16. Marks of 17 and above will be awarded for work addressing all the basic requirements and going further in terms of (one or more of):

    • Evidence of an in-depth consideration of data types and constraints;

    • Relevant and interesting new queries and views;

    • Good style in using SQL, perhaps by the use of joins or views;

    • Report demonstrating excellent understanding of SQL, of the relationship between conceptual and logical data models and their SQL implementations;

    • Any other work which goes out of the basic specifications given to demonstrate excellence in understanding and/or technique.


Policies and Guidelines

Marking

See also the standard mark descriptors in the School Student Handbook, which apply as usual: https://info.cs.st-andrews.ac.uk/student-handbook/learning-teaching/feedback. html#Mark_Descriptors


Lateness

The standard penalty for late submission applies (Scheme B: 1 mark per 8 hour period, or part thereof): https://info.cs.st-andrews.ac.uk/student-handbook/learning-teaching/assessment. html#Lateness_Penalties


Good Academic Practice

The University policy on Good Academic Practice applies:

https://www.st-andrews.ac.uk/students/rules/academicpractice/




























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