07
Thu, Nov
7 New Articles

RPG Academy: Database Modernization - Methodology, Part 9

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

Let’s explore another of DB2’s advanced functionalities: the identity column. This is one of the most interesting and simultaneously least-used functionalities of DB2. Keep reading to find out how to use it.

Last time around, I talked about column-level encryption, a great DB2 functionality that allows you protect sensitive columns with a password by using just a couple of SQL statements.

The other functionality I’d like to talk about is so simple and has been around for so long that I consider it amazing that most shops don’t use it. One of the simplest pieces of business logic that can be embedded into your DB2 object definitions is automated key generation. Almost all applications have code that generates a key value for an item ID, an invoice, or a customer number and then inserts that value into a database table for storage. Why not just use DB2’s native functionality to generate that value as it inserts the row into the table?

Automated Key Generation Using Identity and Sequence

That is exactly what the Identity column attribute and sequence object can provide. Let DB2 handle the key generation and locking/serialization of that value, so you can concentrate on real business logic. Using native I/O, the relative record number (RRN) can be used to access exactly one selected record. SQL provides a scalar function RRN (file) to determine the relative record number; however, it is not possible to generate an index over the relative record number. To prevent SQL from reading the whole table to find the ID, you can add a column to hold the unique identifier and then build an index over this column. You have three possibilities at your disposal:

  • Identity column attribute
  • Sequence object
  • ROWID data type

Identity Column

Let’s start with the Identity column attribute. This column’s type must be a numeric data type, like an integer or a decimal. Optionally, you can also specify values for the start, minimal, and maximal values, as well as an increment step. There are two ways to create an identity column:

  • If you use the IBM i Navigator to create the table, selectSet as identity columnin theNew Columnwindow.
  • If you use a script tool (such as STRSQL, Run SQL Scripts, or any of the other tools I mentioned in the “Tools of the Trade” subseries of “SQL 101,” which you can find here), just add a column with GENERATED ALWAYS AS IDENTITY after the data type. For instance, adding an identity column to the EMPLOYEE_MASTER table would be done something like this:

CREATE TABLE MYAPPDB/EMPLOYEE_MASTER

      (EMPLOYEE_ID INTEGER GENERATED ALWAYS AS IDENTITY

      , (some more columns here...))

The database engine will manage the value of each new record for you, so there’s no need to keep data areas with counters or any other solution. Cool, isn’t it? But wait, there’s more!

Sequence Objects

Here’s how the second item on the list, the sequence object, works: The sequence object allows automatic generation of values, just like the identity column. However, a sequence object is a global and standalone object that can be used by any tables in the same database, unlike an identity column attribute, which is bound to a specific table. Here’s how to create a sequence object named ORDER_SEQ:

CREATE SEQUENCE   ORDER_SEQ

      START WITH       10

      INCREMENT BY      10

When inserting a row, the sequence number must be determined through the NEXT VALUE FOR SEQUENCE instruction. For example, if I want to insert a row in the ORDER_HEADER table using a value from the sequence object, I just need to type this:

INSERT INTO       MYAPPDB/ORDER_HEADER (ORDNUM, CLINUM)

VALUES(NEXT VALUE FOR ORDER_SEQ, <client number goes here> )

Because the sequence is an independent object and not directly tied to a particular table or column, it can be used with multiple tables and columns (this can be both a blessing and a curse, so choose wisely which sequence you’re using for which table/column). Because of its independence from tables, a sequence can easily be changed through the SQL statement ALTER SEQUENCE. The ALTER SEQUENCE statement only generates or updates the sequence object, and it doesn’t change any data.

Neat, right?

Coming Up Next

Unfortunately, that’s all the time I have for now. Next time around, I’ll discuss ROWID, the third way to generate a unique key for a record. Until then, feel free to suggest other ways to automatically generate a record key or simply share your experience with the abovementioned methods.

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

BLOG COMMENTS POWERED BY DISQUS

LATEST COMMENTS

Support MC Press Online

$

Book Reviews

Resource Center

  • SB Profound WC 5536 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. You can find Part 1 here. In Part 2 of our free Node.js Webinar Series, Brian May teaches you the different tooling options available for writing code, debugging, and using Git for version control. Brian will briefly discuss the different tools available, and demonstrate his preferred setup for Node development on IBM i or any platform. Attend this webinar to learn:

  • 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 company are not aligned with the current IT environment.

  • SB HelpSystems ROBOT Generic IBM announced the E1080 servers using the latest Power10 processor in September 2021. The most powerful processor from IBM to date, Power10 is designed to handle the demands of doing business in today’s high-tech atmosphere, including running cloud applications, supporting big data, and managing AI workloads. But what does Power10 mean for your data center? In this recorded webinar, IBMers Dan Sundt and Dylan Boday join IBM Power Champion Tom Huntington for a discussion on why Power10 technology is the right strategic investment if you run IBM i, AIX, or Linux. In this action-packed hour, Tom will share trends from the IBM i and AIX user communities while Dan and Dylan dive into the tech specs for key hardware, including:

  • Magic MarkTRY 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. Make sure your data survives when catastrophe hits. Request your trial now!  Request Now.

  • SB HelpSystems ROBOT GenericForms of ransomware has been around for over 30 years, and with more and more organizations suffering attacks each year, it continues to endure. What has made ransomware such a durable threat and what is the best way to combat it? In order to prevent ransomware, organizations must first understand how it works.

  • SB HelpSystems ROBOT GenericIT security is a top priority for businesses around the world, but most IBM i pros don’t know where to begin—and most cybersecurity experts don’t know IBM i. In this session, Robin Tatam explores the business impact of lax IBM i security, the top vulnerabilities putting IBM i at risk, and the steps you can take to protect your organization. If you’re looking to avoid unexpected downtime or corrupted data, you don’t want to miss this session.

  • SB HelpSystems ROBOT GenericCan you trust all of your users all of the time? A typical end user receives 16 malicious emails each month, but only 17 percent of these phishing campaigns are reported to IT. Once an attack is underway, most organizations won’t discover the breach until six months later. A staggering amount of damage can occur in that time. Despite these risks, 93 percent of organizations are leaving their IBM i systems vulnerable to cybercrime. In this on-demand webinar, IBM i security experts Robin Tatam and Sandi Moore will reveal:

  • FORTRA Disaster protection is vital to every business. Yet, it often consists of patched together procedures that are prone to error. From automatic backups to data encryption to media management, Robot automates the routine (yet often complex) 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:

  • FORTRAManaging messages on your IBM i can be more than a full-time job if you have to do it manually. Messages need a response and resources must be monitored—often over multiple systems and across platforms. 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:

  • FORTRAThe thought of printing, distributing, and storing iSeries reports manually may reduce you to tears. Paper and labor costs associated with report generation can spiral out of control. Mountains of paper threaten to swamp your files. Robot 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:

  • FORTRAFor over 30 years, Robot has been a leader in systems management for IBM i. With batch job creation and scheduling at its core, the Robot Job Scheduling Solution reduces the opportunity for human error and helps you maintain service levels, automating even the biggest, most complex runbooks. Manage your job schedule with the Robot Job Scheduling Solution. Key features include:

  • LANSA Business 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.

  • 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:

  • LANSASupply Chain is becoming increasingly complex and unpredictable. From raw materials for manufacturing to food supply chains, the journey from source to production to delivery to consumers is marred with inefficiencies, manual processes, shortages, recalls, counterfeits, and scandals. In this webinar, we discuss how:

  • The MC Resource Centers bring you the widest selection of white papers, trial software, and on-demand webcasts for you to choose from. >> Review the list of White Papers, Trial Software or On-Demand Webcast at the MC Press Resource Center. >> Add the items to yru Cart and complet he checkout process and submit

  • Profound Logic 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.

  • SB Profound WC 5536Join us for this hour-long webcast that will explore:

  • Fortra IT managers hoping to find new IBM i talent are discovering that the pool of experienced RPG programmers and operators or administrators with intimate knowledge of the operating system and the applications that run on it is small. This begs the question: How will you manage the platform that supports such a big part of your business? 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: