Sidebar

Improve Your Database with Normalization

DB2
Typography
  • Smaller Small Medium Big Bigger
  • Default Helvetica Segoe Georgia Times

A quick guide to the basics of database normalization—a critical step in refreshing an older IBM i database

Editor's note: This article is excerpted from chapter 5 of SQL for IBM i: A Database Modernization Guide, by Rafael Victoria-Pereira.

Most people take a quick look at the normal forms definitions—the “steps” to achieve normalization Nirvana—and dismiss the whole thing as being an academic and convoluted waste of time. Actually, normalization is, for the most part, easy and mostly common sense with some business knowledge thrown in. Once you understand the fundamental concepts, you’ll see that it’s useful and a great way to tackle aging and “broken” databases. Let me start by introducing a few key concepts that will be used later to define each normal form.

Data Anomalies

UMADB [the example database] is already suffering from data anomalies: I’ve told you about the different “versions” of the student data found in several tables. This is being caused by structural problems in the database, which I’ll try to fix in this normalization process. But before we go any further, it’s important to define what we’re trying to fix. So, let’s take a moment to consider the different types of data anomalies, starting with the insert anomaly.

This type of anomaly occurs when a child record is inserted without a link to the parent record. For instance, creating a Grades record for a student that doesn’t exist; this can be a simple misspelling error, but it will cause an insert anomaly and put the database into an inconsistent state. However, the same thing can happen when you’re updating data: unless you have the proper safeguards in place, you can accidentally break the link between two tables, thus leaving the child table record “orphaned.” This is called an update anomaly.

Imagine that you’re updating the student information in the Classes table and inadvertently change the course name. Doing so causes the record to become orphaned, because the link to the Courses table will be compromised.

Finally, a delete anomaly occurs when you delete a parent table’s record and don’t do the same with the child’s. Because UMADB tables’ relationships are flimsy and defined at the application level, it’s very easy to mess up the database with a couple of DML statements.

These are the anomalies that we’d like to prevent. We’ll do that by applying the normal forms, as I mentioned earlier. But before that, there’s some mathematical terms you need to know.

Some Boring, Yet Important, Math Jargon

Let’s start with the simplest of them all: dependency. Dependency can come in many forms, but the easiest to understand is functional dependency: Y is functionally dependent on X if the value of Y is determined by X. In other words, if Y = X +1, the value of X will determine the resultant value of Y. Thus, Y is dependent on X as a function of the value of X.

Imagine that the university keeps a currency rates table because of its student exchange program. A sample of this table’s content, at a given time (so disregard the fact that the rates are not current), is shown in Table 1.

Table 1: Currency rates table

Currency_Code

Name

Rate

Country Name

JPY

Yen

101.689

Japan

CAD

Dollar

1.31075

Canada

AUD

Dollar

1.3217

Australia

INR

Rupee

66.725

India

NZD

Dollar

1.38535

New Zealand

GBP

Pound

0.7558

Great Britain

This table demonstrates functional dependency between the Name and Currency_Code columns: the currency name being Yen depends on the currency code being JPY.

The next notion is determinant. The determinant in the description of functional dependency in the previous paragraph is X, because X determines the value Y (at least partially because 1 is added to X as well). In Table 1, the determinant of the currency name being Rupee is the value of the currency code being INR. This means that the determinant is the currency code column. In other words, a determinant is the inversion or opposite of functional dependency.

So far, so good. Now it gets more interesting ... I hope. A transitive dependence describes the indirect dependency of a column on another: for instance, Z is transitively dependent on X when X determines Y and Y determines Z. Transitive dependence thus describes that Z is indirectly dependent on X through its relationship with Y. In Table 1, the foreign exchange rates in the Rate column (against the U.S. dollar) are dependent on the currency name (Name column). The currency name, in turn, is dependent on the country name (Country Name column). Thus, the rate is dependent on the currency, which is in turn dependent on the country name; therefore, the Rate column is transitively dependent on the Country Name column.

The next concept is something that you’re probably already familiar with: a candidate key, also known as potential or permissible key, is a field or combination of fields that can act as a primary key field for a table—thus uniquely identifying each record in the table. Most of the tables that resulted from the adjustments performed in the previous chapter have an ID column, which fits all the requirements for being a candidate key: each ID is unique within the table and is, by itself, enough to identify a record.

These ID columns actually eliminated all full functional dependencies on UMADB’s tables, because all the columns of each table depend on the primary key and this primary key is not a composite key—it’s formed by the ID column alone. For instance, if the Classes table didn’t have an ID field and its primary key was formed by the class name and class year, we could say that the course name was not fully functionally dependent of the table’s primary key, because the course name would depend only on the class name and not the class year.

However, the adjustments performed on the previous chapter didn’t solve all the database’s problems. One of the most common (and annoying, if you ask me) problems is the multi-valued dependency that exists on the Subjects_Taught column of the Teachers table. This column contains multiple values, separated by commas. These values depend on the table’s primary key as a whole. If you want to do anything with one of these values, you’ll have to isolate it from the rest of the values on the column; even so, the whole process is prone to error.

The last type of dependency doesn’t happen very often, but when it does, it’s a nightmare to untangle: cyclic dependency means that X is dependent on Y, which in turn is also dependent on X, directly or indirectly. Cyclic dependence, therefore, indicates a logically circular pattern of interdependence. Cyclic dependence typically occurs with tables containing a composite primary key of three or more fields (for example, where three fields are related in pairs to each other). In other words, X relates to Y, Y relates to Z, and X relates to Z. Ultimately Z relates back to X. This is not very common, but I’ve seen it happen in tables with complex keys and multiple identifying relationships to other equally complex tables.

These notions may seem farfetched and pointless now, but you’ll see how the normal forms relate to them and how this can be of use when “tidying up” a database.

Introducing the Normal Forms, Academic Version

The steps to achieving Nirvana are long and hard ... wait, wrong book. No, they’re actually simple and a very acceptable. A normalization pseudo-Nirvana state can be achieved with only three steps, explained next. Unlike the steps in other paths to enlightenment, these have logical, cold, and simple names (they were defined by the academic community, so what else could we expect?).

  • First normal form (1NF)—Eliminate repeating groups so that all records in all tables can be identified uniquely by a primary key in each table. In other words, all fields other than the primary key must depend on the primary key.
  • Second normal form (2NF)—All non-key values must be fully functionally dependent on the primary key. No partial dependencies are allowed. A partial dependency exists when a field is fully dependent on a part of a composite primary key.
  • Third normal form (3NF)—Eliminate transitive dependencies, meaning that a field is indirectly determined by the primary key. This is because the field is functionally dependent on another field, whereas the other field is dependent on the primary key.

We’ll be implementing these three steps in UMADB during this chapter, but the normalization path doesn’t end here. It goes further with (even more) convoluted requirements:

  • Boyce-Codd normal form (BCNF)—Every determinant in a table is a candidate key. If there is only one candidate key, BCNF and 3NF are one and the same.
  • Fourth normal form (4NF)—Eliminate multiple sets of multi-valued dependencies.
  • Fifth normal form (5NF)—Eliminate cyclic dependencies. 5NF is also known as projection normal form (PJNF).
  • Domain key normal form (DKNF)—DKNF is the ultimate application of normalization and is more a measurement of conceptual state, as opposed to a transformation process in itself. It’s normalization Nirvana.

You might be wondering why we’ll stop at 3NF when the rest of the normal forms seem accessible. Well, the problem is that the higher the normalization state is, the harder it gets to query the database. This happens because higher normalization states cause more data fragmentation (read: more tables), and this affects performance. And we all know that a database with poor performance is not really useful. That’s enough theory; let’s apply the normal forms to UMADB!

Normalizing UMADB to 3NF

1NF is easy to understand, but sometimes it’s not so easy to apply. In UMADB’s case, a quick review of the tables shows that only the Classes table contains repeating groups of columns: the class name and class year columns have repeating values, one per each student who attended a certain class in a certain year. The first step is fixing this issue, by “exploding” this table into three tables and adding information: one of the class definitions, which will contain the class name; a link to the course table and a description; table two with the class for a given year, containing the teacher name; and finally, a third table for student enrollment in that class/year combination.

2NF is somewhat similar to 1NF, but at value level, as opposed to 1NF’s column level. There’s only one example of columns holding multiple values: the Subjects_Taught column in the Teachers table. The logical thing to do would be to create a many-to-many relationship, because a teacher can teach many subjects and a subject can be taught by many teachers, but in practice many-to-many relationships should be avoided at all costs. They are conceptually sane, but hard to understand and maintain in a real database. A many-to-many relationship would imply creating a Subjects table and linking it to the existing Teachers table. Instead, we’ll include an intermediate table, named Subjects_Taught, and create one-to-many relationships with both the existing Teachers table and the new Subjects table.

3NF is not so easy to explain. Even if you understand what a transitive dependency is, it can be hard to identify it in a database. Let me give you a hand: I started this chapter by referring to some duplicate data across the database and went on to explain how and why this can cause data anomalies. The student data exists in multiple tables, but, in most cases, it shouldn’t because it doesn’t depend directly on the table’s primary key. For instance, a student’s home address shouldn’t depend on the class he/she is taking. Instead, it should depend on the student information stored in the Students table. However, a closer look at the Students and Teachers tables reveals that they have a lot of information in common—after all, both students and teachers are people. This means that it might be a good idea to strip these tables of the information about a person that they contain and centralize that data in a new Persons table. Naturally, the partial information contained in the Classes table should also be eliminated and replaced with a link to the respective student record.

We’ll also create new tables for the Department (only its name exists in the Courses table, which can lead to confusing situations) and Teacher Rank, to avoid inconsistencies. Finally, we’ll introduce referential integrity to this database (at the moment, all the connections between tables are kept at the application level, and, from what we’ve seen, it’s not working properly) by replacing the weak links (name references, mostly, such as the student name in the Classes table) with proper foreign keys.

In summary, here’s what we’ll have to do:

  1. Create new tables for Class Definitions, Classes per Year, Class Enrollment, Subjects, Subjects Taught, Persons, Departments, and Teacher Ranks.
  2. Remove duplicate columns, related with student data, in the Students, Teachers, and Classes tables.
  3. Create proper foreign keys to link all the “informally linked” existing tables and link the new tables as well.

We could continue to change the tables the same way we’ve been doing so far—using DROP and CREATE TABLE statements. However, there are a lot of changes and it’s going to be hard to keep track of everything. Instead, we’ll “do it like the pros” and use a data-modeling tool.

 

Rafael Victoria-Pereira

Rafael Victória-Pereira has more than 20 years of IBM i experience as a programmer, analyst, and manager. Over that period, he has been an active voice in the IBM i community, encouraging and helping programmers transition to ILE and free-format RPG. Rafael has written more than 100 technical articles about topics ranging from interfaces (the topic for his first book, Flexible Input, Dazzling Output with IBM i) to modern RPG and SQL in his popular RPG Academy and SQL 101 series on mcpressonline.com and in his books Evolve Your RPG Coding and SQL for IBM i: A Database Modernization Guide. Rafael writes in an easy-to-read, practical style that is highly popular with his audience of IBM technology professionals.

Rafael is the Deputy IT Director - Infrastructures and Services at the Luis Simões Group in Portugal. His areas of expertise include programming in the IBM i native languages (RPG, CL, and DB2 SQL) and in "modern" programming languages, such as Java, C#, and Python, as well as project management and consultancy.


MC Press books written by Rafael Victória-Pereira available now on the MC Press Bookstore.

Evolve Your RPG Coding: Move from OPM to ILE...and Beyond Evolve Your RPG Coding: Move from OPM to ILE...and Beyond
Transition to modern RPG programming with this step-by-step guide through ILE and free-format RPG, SQL, and modernization techniques.
List Price $79.95

Now On Sale

Flexible Input, Dazzling Output with IBM i Flexible Input, Dazzling Output with IBM i
Uncover easier, more flexible ways to get data into your system, plus some methods for exporting and presenting the vital business data it contains.
List Price $79.95

Now On Sale

SQL for IBM i: A Database Modernization Guide SQL for IBM i: A Database Modernization Guide
Learn how to use SQL’s capabilities to modernize and enhance your IBM i database.
List Price $79.95

Now On Sale

More Articles By This Author
Related Articles
BLOG COMMENTS POWERED BY DISQUS

LATEST COMMENTS

Support MC Press Online

RESOURCE CENTER

  • WHITE PAPERS

  • WEBCAST

  • TRIAL SOFTWARE

  • White Paper: Node.js for Enterprise IBM i Modernization

    SB Profound WP 5539

    If your business is thinking about modernizing your legacy IBM i (also known as AS/400 or iSeries) applications, you will want to read this white paper first!

    Download this paper and learn how Node.js can ensure that you:
    - Modernize on-time and budget - no more lengthy, costly, disruptive app rewrites!
    - Retain your IBM i systems of record
    - Find and hire new development talent
    - Integrate new Node.js applications with your existing RPG, Java, .Net, and PHP apps
    - Extend your IBM i capabilties to include Watson API, Cloud, and Internet of Things


    Read Node.js for Enterprise IBM i Modernization Now!

     

  • Profound Logic Solution Guide

    SB Profound WP 5539More than ever, there is a demand for IT to deliver innovation.
    Your IBM i has been an essential part of your business operations for years. However, your organization may struggle to maintain the current system and implement new projects.
    The thousands of customers we've worked with and surveyed state that expectations regarding the digital footprint and vision of the companyare not aligned with the current IT environment.

    Get your copy of this important guide today!

     

  • 2022 IBM i Marketplace Survey Results

    Fortra2022 marks the eighth edition of the IBM i Marketplace Survey Results. Each year, Fortra captures data on how businesses use the IBM i platform and the IT and cybersecurity initiatives it supports.

    Over the years, this survey has become a true industry benchmark, revealing to readers the trends that are shaping and driving the market and providing insight into what the future may bring for this technology.

  • Brunswick bowls a perfect 300 with LANSA!

    FortraBrunswick is the leader in bowling products, services, and industry expertise for the development and renovation of new and existing bowling centers and mixed-use recreation facilities across the entertainment industry. However, the lifeblood of Brunswick’s capital equipment business was running on a 15-year-old software application written in Visual Basic 6 (VB6) with a SQL Server back-end. The application was at the end of its life and needed to be replaced.
    With the help of Visual LANSA, they found an easy-to-use, long-term platform that enabled their team to collaborate, innovate, and integrate with existing systems and databases within a single platform.
    Read the case study to learn how they achieved success and increased the speed of development by 30% with Visual LANSA.

     

  • Progressive Web Apps: Create a Universal Experience Across All Devices

    LANSAProgressive Web Apps allow you to reach anyone, anywhere, and on any device with a single unified codebase. This means that your applications—regardless of browser, device, or platform—instantly become more reliable and consistent. They are the present and future of application development, and more and more businesses are catching on.
    Download this whitepaper and learn:

    • How PWAs support fast application development and streamline DevOps
    • How to give your business a competitive edge using PWAs
    • What makes progressive web apps so versatile, both online and offline

     

     

  • The Power of Coding in a Low-Code Solution

    LANSAWhen it comes to creating your business applications, there are hundreds of coding platforms and programming languages to choose from. These options range from very complex traditional programming languages to Low-Code platforms where sometimes no traditional coding experience is needed.
    Download our whitepaper, The Power of Writing Code in a Low-Code Solution, and:

    • Discover the benefits of Low-code's quick application creation
    • Understand the differences in model-based and language-based Low-Code platforms
    • Explore the strengths of LANSA's Low-Code Solution to Low-Code’s biggest drawbacks

     

     

  • Why Migrate When You Can Modernize?

    LANSABusiness users want new applications now. Market and regulatory pressures require faster application updates and delivery into production. Your IBM i developers may be approaching retirement, and you see no sure way to fill their positions with experienced developers. In addition, you may be caught between maintaining your existing applications and the uncertainty of moving to something new.
    In this white paper, you’ll learn how to think of these issues as opportunities rather than problems. We’ll explore motivations to migrate or modernize, their risks and considerations you should be aware of before embarking on a (migration or modernization) project.
    Lastly, we’ll discuss how modernizing IBM i applications with optimized business workflows, integration with other technologies and new mobile and web user interfaces will enable IT – and the business – to experience time-added value and much more.

     

  • UPDATED: Developer Kit: Making a Business Case for Modernization and Beyond

    Profound Logic Software, Inc.Having trouble getting management approval for modernization projects? The problem may be you're not speaking enough "business" to them.

    This Developer Kit provides you study-backed data and a ready-to-use business case template to help get your very next development project approved!

  • What to Do When Your AS/400 Talent Retires

    FortraIT managers hoping to find new IBM i talent are discovering that the pool of experienced RPG programmers and operators or administrators is small.

    This guide offers strategies and software suggestions to help you plan IT staffing and resources and smooth the transition after your AS/400 talent retires. Read on to learn:

    • Why IBM i skills depletion is a top concern
    • How leading organizations are coping
    • Where automation will make the biggest impact

     

  • Node.js on IBM i Webinar Series Pt. 2: Setting Up Your Development Tools

    Profound Logic Software, Inc.Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application. In Part 2, Brian May teaches you the different tooling options available for writing code, debugging, and using Git for version control. Attend this webinar to learn:

    • Different tools to develop Node.js applications on IBM i
    • Debugging Node.js
    • The basics of Git and tools to help those new to it
    • Using NodeRun.com as a pre-built development environment

     

     

  • Expert Tips for IBM i Security: Beyond the Basics

    SB PowerTech WC GenericIn this session, IBM i security expert Robin Tatam provides a quick recap of IBM i security basics and guides you through some advanced cybersecurity techniques that can help you take data protection to the next level. Robin will cover:

    • Reducing the risk posed by special authorities
    • Establishing object-level security
    • Overseeing user actions and data access

    Don't miss this chance to take your knowledge of IBM i security beyond the basics.

     

     

  • 5 IBM i Security Quick Wins

    SB PowerTech WC GenericIn today’s threat landscape, upper management is laser-focused on cybersecurity. You need to make progress in securing your systems—and make it fast.
    There’s no shortage of actions you could take, but what tactics will actually deliver the results you need? And how can you find a security strategy that fits your budget and time constraints?
    Join top IBM i security expert Robin Tatam as he outlines the five fastest and most impactful changes you can make to strengthen IBM i security this year.
    Your system didn’t become unsecure overnight and you won’t be able to turn it around overnight either. But quick wins are possible with IBM i security, and Robin Tatam will show you how to achieve them.

  • Security Bulletin: Malware Infection Discovered on IBM i Server!

    SB PowerTech WC GenericMalicious programs can bring entire businesses to their knees—and IBM i shops are not immune. It’s critical to grasp the true impact malware can have on IBM i and the network that connects to it. Attend this webinar to gain a thorough understanding of the relationships between:

    • Viruses, native objects, and the integrated file system (IFS)
    • Power Systems and Windows-based viruses and malware
    • PC-based anti-virus scanning versus native IBM i scanning

    There are a number of ways you can minimize your exposure to viruses. IBM i security expert Sandi Moore explains the facts, including how to ensure you're fully protected and compliant with regulations such as PCI.

     

     

  • Encryption on IBM i Simplified

    SB PowerTech WC GenericDB2 Field Procedures (FieldProcs) were introduced in IBM i 7.1 and have greatly simplified encryption, often without requiring any application changes. Now you can quickly encrypt sensitive data on the IBM i including PII, PCI, PHI data in your physical files and tables.
    Watch this webinar to learn how you can quickly implement encryption on the IBM i. During the webinar, security expert Robin Tatam will show you how to:

    • Use Field Procedures to automate encryption and decryption
    • Restrict and mask field level access by user or group
    • Meet compliance requirements with effective key management and audit trails

     

  • Lessons Learned from IBM i Cyber Attacks

    SB PowerTech WC GenericDespite the many options IBM has provided to protect your systems and data, many organizations still struggle to apply appropriate security controls.
    In this webinar, you'll get insight into how the criminals accessed these systems, the fallout from these attacks, and how the incidents could have been avoided by following security best practices.

    • Learn which security gaps cyber criminals love most
    • Find out how other IBM i organizations have fallen victim
    • Get the details on policies and processes you can implement to protect your organization, even when staff works from home

    You will learn the steps you can take to avoid the mistakes made in these examples, as well as other inadequate and misconfigured settings that put businesses at risk.

     

     

  • The Power of Coding in a Low-Code Solution

    SB PowerTech WC GenericWhen it comes to creating your business applications, there are hundreds of coding platforms and programming languages to choose from. These options range from very complex traditional programming languages to Low-Code platforms where sometimes no traditional coding experience is needed.
    Download our whitepaper, The Power of Writing Code in a Low-Code Solution, and:

    • Discover the benefits of Low-code's quick application creation
    • Understand the differences in model-based and language-based Low-Code platforms
    • Explore the strengths of LANSA's Low-Code Solution to Low-Code’s biggest drawbacks

     

     

  • Node Webinar Series Pt. 1: The World of Node.js on IBM i

    SB Profound WC GenericHave you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application.
    Part 1 will teach you what Node.js is, why it's a great option for IBM i shops, and how to take advantage of the ecosystem surrounding Node.
    In addition to background information, our Director of Product Development Scott Klement will demonstrate applications that take advantage of the Node Package Manager (npm).
    Watch Now.

  • The Biggest Mistakes in IBM i Security

    SB Profound WC Generic The Biggest Mistakes in IBM i Security
    Here’s the harsh reality: cybersecurity pros have to get their jobs right every single day, while an attacker only has to succeed once to do incredible damage.
    Whether that’s thousands of exposed records, millions of dollars in fines and legal fees, or diminished share value, it’s easy to judge organizations that fall victim. IBM i enjoys an enviable reputation for security, but no system is impervious to mistakes.
    Join this webinar to learn about the biggest errors made when securing a Power Systems server.
    This knowledge is critical for ensuring integrity of your application data and preventing you from becoming the next Equifax. It’s also essential for complying with all formal regulations, including SOX, PCI, GDPR, and HIPAA
    Watch Now.

  • Comply in 5! Well, actually UNDER 5 minutes!!

    SB CYBRA PPL 5382

    TRY the one package that solves all your document design and printing challenges on all your platforms.

    Produce bar code labels, electronic forms, ad hoc reports, and RFID tags – without programming! MarkMagic is the only document design and print solution that combines report writing, WYSIWYG label and forms design, and conditional printing in one integrated product.

    Request your trial now!

  • Backup and Recovery on IBM i: Your Strategy for the Unexpected

    FortraRobot automates the routine tasks of iSeries backup and recovery, saving you time and money and making the process safer and more reliable. Automate your backups with the Robot Backup and Recovery Solution. Key features include:
    - Simplified backup procedures
    - Easy data encryption
    - Save media management
    - Guided restoration
    - Seamless product integration
    Make sure your data survives when catastrophe hits. Try the Robot Backup and Recovery Solution FREE for 30 days.

  • Manage IBM i Messages by Exception with Robot

    SB HelpSystems SC 5413Managing messages on your IBM i can be more than a full-time job if you have to do it manually. How can you be sure you won’t miss important system events?
    Automate your message center with the Robot Message Management Solution. Key features include:
    - Automated message management
    - Tailored notifications and automatic escalation
    - System-wide control of your IBM i partitions
    - Two-way system notifications from your mobile device
    - Seamless product integration
    Try the Robot Message Management Solution FREE for 30 days.

  • Easiest Way to Save Money? Stop Printing IBM i Reports

    FortraRobot automates report bursting, distribution, bundling, and archiving, and offers secure, selective online report viewing.
    Manage your reports with the Robot Report Management Solution. Key features include:

    - Automated report distribution
    - View online without delay
    - Browser interface to make notes
    - Custom retention capabilities
    - Seamless product integration
    Rerun another report? Never again. Try the Robot Report Management Solution FREE for 30 days.

  • Hassle-Free IBM i Operations around the Clock

    SB HelpSystems SC 5413For over 30 years, Robot has been a leader in systems management for IBM i.
    Manage your job schedule with the Robot Job Scheduling Solution. Key features include:
    - Automated batch, interactive, and cross-platform scheduling
    - Event-driven dependency processing
    - Centralized monitoring and reporting
    - Audit log and ready-to-use reports
    - Seamless product integration
    Scale your software, not your staff. Try the Robot Job Scheduling Solution FREE for 30 days.