Practical DB2: Database Field-Naming Conventions

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

The good thing about naming conventions is that there are so many of them, and database field naming is just one of those areas of convention contention.

Put three programmers in a room to define a database and you'll end up with at least four different sets of naming conventions. And it won't be quick, either, no matter how much experience you have. I can't count the number of databases I've helped design over the years, yet I still find myself in a room sitting for hours every time I have to work on another one. Each database has its own idiosyncrasies, but a few areas are relatively common among all databases. This article will address one of the fundamental issues: field names.


Identifying the Business Requirement

Even though it seems like a pretty technical pursuit, you should think like an analyst when creating your programming conventions: Identify the business requirement, establish some success criteria, and then meet that goal. In the case of field-naming conventions, my goal is twofold: Make it easy to get data into my database, and make it easy to get data out. Naming conventions are becoming more important rather than less; increasingly, we're seeing users accessing data through ad hoc query tools, and those conventions make it easier on them as well. Today, I am going to use a very specific example to prove just how important those conventions can be. The example is quite straightforward: I'm going to add an order header record. When creating the record, I'm going to initialize several fields with values from the customer master. And while the example will be very simple, it will show how good naming conventions scale quickly and easily.



Over the years, we've seen more and more integration of SQL and traditional database I/O, but field naming is one area where the two don't seem to always mesh well. IBM has done everything it can to allow the two to live together in harmony, but real consistency requires an attention to detail that sometimes just doesn't fall within our time frame. I absolutely believe that the benefits of DDL definition over DDS definition far outweigh any drawbacks, but those benefits aren't completely risk-free. To me, the biggest problem with SQL is that it lends itself to a very ad hoc development environment, and you have to work hard to not let yourself be caught up in it. The ability to add a field named EXTRA_INFO_FOR_JANET with a simple SQL statement has some significant ramifications, and I'll address those in a follow-up article. For today, I'm going to focus on DDS environments.


To Refer or Not to Refer

Today's example will use a field reference file, albeit a very abbreviated one. I think field reference files are a critical component to any good database design, and I hope to spend more time on the concept a little later. Here's our reference file, named REFFILPF:


R RREFFIL                                          


NAME        30        TEXT('NAME')          

ORNO        10S 0      TEXT('ORDER NUMBER')  

ORDTYP      1A      TEXT('ORDER TYPE')    

PHONE        15        TEXT('PHONE NUMBER')  

ADDR        30         TEXT('ADDRESS')        

CITY        25        TEXT('CITY')          

STATE        3        TEXT('STATE')          

ZIP          9        TEXT('ZIP CODE')      

PHONE        15        TEXT('PHONE')          

EMAIL        64        TEXT('EMAIL ADDRESS')  


The field reference file defines your database attributes at a very basic level: customer number, address, phone number. The basic lengths and types are here. Other files then reference those fields in their definitions. Here's our customer master file, CUSMASPF:



R RCUSMAS                                    

CMCUST   R            REFFLD('CUST')    

CMNAME   R            REFFLD('NAME')    

CMADDR1   R            REFFLD('ADDR')    

CMADDR2   R            REFFLD('ADDR')    

CMCITY   R            REFFLD('CITY')    

CMSTATE   R            REFFLD('STATE')  

CMZIP     R            REFFLD('ZIP')    

CMPHONE   R            REFFLD('PHONE')  

CMFAX     R            REFFLD('FAX')    

CMEMAIL   R            REFFLD('EMAIL')  


You'll probably notice a couple of things right off the bat. First, I use a two-character prefix for every field. This prefix identifies the file name. As we'll see later, it's not strictly necessary, and in fact there is a school of thought that eschews prefixes. Personally, I prefer them because it allows old-school programmers to use the files without a chance of collision. There are nearly 1,000 of these prefixes, so you ought to have no problem coming up with unique identifiers for each database file. Once you've made that decision, field naming becomes quite simple: The name of the field in the database file is simply the name of the referenced field appended to the file's prefix.


You probably notice one anomaly here. While there is only one address field in the reference file, we have two address fields in the customer master. That's not a problem; we create fields CMADDR1 and CMADDR2, but both refer to the same ADDR field in the field reference file. While we try to keep the field names consistent, exceptions like this are very easy to handle. OK, this example also has an order header, so let's define that next:



R RORDHDR                                    

OHORNO   R            REFFLD('ORNO')    


OHCUST   R            REFFLD('CUST')    

OHNAME   R            REFFLD('NAME')    

OHPHONE   R            REFFLD('PHONE')  


Look closely and you'll see several fields that refer to the same fields as fields in the customer master. This is no accident; the design for this particular database calls for the customer name and phone number to be included in the order header. It may be that it has to be modified under certain circumstances, or it just may have to be there for other processing. Whatever the case, you can see that these fields will need to be populated from the corresponding fields in the customer master.


And Now for the Programming Magic

Sometimes, the preparation is more dramatic than the payoff, and this is probably one of those cases. The code that I'm going to show you is really very simple.


ctl-opt dftactgrp(*no) actgrp(*new);      


dcl-f CUSMASPF keyed;                    

dcl-f ORDHDRPF usage(*output);            


dcl-pi *n;                                

iCust like(dsORDHDR.CUST);              

iOrno like(dsORDHDR.ORNO);              



dcl-ds dsCUSMAS extname('CUSMASPF':*input)

prefix('':2) qualified;                


dcl-ds dsORDHDR extname('ORDHDRPF':*output)

prefix('':2) qualified inz;            



dsORDHDR.ORNO = iORNO;                    

chain (iCUST) CUSMASPF dsCUSMAS;          

eval-corr dsORDHDR = dsCUSMAS;            

write RORDHDR dsORDHDR;                  



The first line is the control options, nothing special there (although in a production environment you probably would be using something other than a *NEW activation group). The next two lines define the files: The customer master is input, the order header is output. The next block of code defines the parameters: The program receives a customer number and an order number. The program is supposed to create an order header for that customer. The next block of code does the setup by creating two data structures suitable for I/O. One is used to read data from the customer master, the other to write data to the order header. The trick is the use of the PREFIX('':2) keyword on both data structures. What this does is remove the first two characters of every field. Now, rather than CMCUST and OHCUST, both data structures simply have the field name CUST. This would normally cause the compiler to have some issues, so in order to avoid a collision, I also had to specify QUALIFIED on both. The one difference is that I also specified INZ on the dsORDHDR data structure; this sets any numeric fields to zeros and avoids decimal data errors.


So now that the setup is all done, the code is pretty anticlimactic. I store the order number in the order header. I then chain to the customer master. The magic is the use of the EVAL-CORR to then move all the fields from dsCUSMAS to dsORDHDR. The fields are CUST, NAME, and PHONE. Then I write the record. That's all there is to it.


Now, you might think that's an awful lot of work to avoid three EVAL statements, and you're right, it is. In this simple situation, the setup probably exceeds the savings. But the payoff comes when I decide I want to add the email address. All I do is add the field OHEMAIL to the ORDHDRPF file and recompile the program. That's it; the move happens automatically. If I need more fields, I just add them and recompile. If I need fields from another file, I just add the file and a corresponding data structure, add the chain, and add another EVAL-CORR. This technique is wonderfully scalable and frankly a lot easier than even SQL.


And it all starts from a good, solid set of field-naming conventions! Next, I'll show how to do much of this same work through DDL rather than DDS.


Joe Pluta

Joe Pluta is the founder and chief architect of Pluta Brothers Design, Inc. He has been extending the IBM midrange since the days of the IBM System/3. Joe uses WebSphere extensively, especially as the base for PSC/400, the only product that can move your legacy systems to the Web using simple green-screen commands. He has written several books, including Developing Web 2.0 Applications with EGL for IBM i, E-Deployment: The Fastest Path to the Web, Eclipse: Step by Step, and WDSC: Step by Step. Joe performs onsite mentoring and speaks at user groups around the country. You can reach him at

MC Press books written by Joe Pluta available now on the MC Press Bookstore.

Developing Web 2.0 Applications with EGL for IBM i Developing Web 2.0 Applications with EGL for IBM i
Joe Pluta introduces you to EGL Rich UI and IBM’s Rational Developer for the IBM i platform.
List Price $39.95

Now On Sale

WDSC: Step by Step WDSC: Step by Step
Discover incredibly powerful WDSC with this easy-to-understand yet thorough introduction.
List Price $74.95

Now On Sale

Eclipse: Step by Step Eclipse: Step by Step
Quickly get up to speed and productivity using Eclipse.
List Price $59.00

Now On Sale



Support MC Press Online





  • 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.


  • 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 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



  • 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.