12
Wed, Jun
4 New Articles

SQL 101: String-Related Functions, Part 1 - Converting Almost Anything to a String

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

SQL provides more, much more, than the aggregate functions discussed in the previous article. This time around, I'll start to explore the scalar functions.

 

There are many scalar functions, ranging from trig functions (yes, they do exist in SQL) to date- and time-handling functions. I'll start with a few scalar functions that allow you to convert almost anything to a string.

 

By definition, a scalar function takes input argument(s) and returns a single value result. A scalar function can be used wherever an expression can be used (for instance, the Select, Where, or Group By clauses of a Select statement).

 

The restrictions on the use of aggregate functions I discussed in the previous article do not apply to scalar functions, because a scalar function is applied to single parameter values rather than to sets of values. The argument of a scalar function can be another function. However, the restrictions that apply to the use of expressions and aggregate functions also apply when an expression or aggregate function is used within a scalar function.

 

There are a lot of scalar functions and IBM keeps adding more with each DB2 enhancement. My initial plan is to address a few of them, namely those related with string- and date-handling, but there are many more, purposely built to handle XML, DataLinks, math, trigonometry, and a lot more. I'll let you, dear reader, take the helm and suggest other types of functions to discuss in this series. Because you probably have no idea what SQL has to offer, it might be easier to explain a problem/situation and I'll try to find the best function or functions to solve it.

 

When I get stuck with a problem that I have no idea how to solve, I usually check out IBM's DB2 for i Reference manual for the complete list of SQL functions. I always find the solution (or at least, the inspiration) I need to tackle the issue at hand.

 

Because there are so many string-related scalar functions, let's divide them into more manageable subsets and address these one by one, starting with the string conversion-related functions. Of these, the ASCII function is certainly the easiest to grasp. It returns the ASCII code value of the leftmost character of the argument as an integer. I'll keep using the same InvMst table introduced in the second article of this series in most of my examples. For instance,

 

SELECT      ASCII(ItemID)

FROM        InvMst

WHERE       ItemID = 'A123'

GROUP BY    ItemID

 

returns 65, because that's the integer value for the ASCII representation of 'A'. SQL also provides a function to perform the inverse operation: CHR. I'll use a system dummy table named SYSDUMMY1 to illustrate the way it works:

 

SELECT            CHR(65)

FROM        SYSIBM.SYSDUMMY1

 

This statement returns 'A', because that's the ASCII representation that corresponds to the 65 integer value. You could go nuts here and do some function nesting; something like SELECT CHR(ASCII('A')) FROM SYSIBM.SYSDUMMY1 would return 'A', because the processing is performed from the inside out, which means that the database engine would evaluate ASCII('A'), return 65 and then would use that as input parameter for the CHR; this in turn would return 'A'. I know this is an idiotic and useless example of function nesting, but it's also a nice way to illustrate the function-nesting concept in SQL.

 

The CHAR function is very similar to RPG's %CHAR BIF: it takes a numeric expression as an input parameter and converts it to the respective string representation. If the expression to be converted is either a Decimal or Floating-point expression, you can specify a second parameterthe decimal separator. You can also use CHAR to convert date/time data types to their string representation; in this case, the second parameter is the format. The possible values are ISO, EUR, USA, and JIS. The table below details each of these possible values.

 

Accepted Formats for Date Conversion Using CHAR

Format Name

Abbreviation

Date Format

Example

International Standards Organization (*ISO)

ISO

'yyyy-mm-dd'

'2014-11-16'

IBM USA standard (*USA)

USA

'mm/dd/yyyy'

'11/16/2014'

IBM European standard (*EUR)

EUR

'dd.mm.yyyy'

'16.11.2014'

Japanese industrial standard Christian era (*JIS)

JIS

'yyyy-mm-dd'

'2014-11-16'

 

 

Here's an example of CHAR's possible use:

 

SELECT            ItemID

, CHAR(ItemQty)

            , CHAR(LotNbr)

            , CHAR(ExpDate, ISO)

FROM        InvMst

WHERE       ItemID = 'A123'

            AND WHID = 333

            AND ShelfID = 77

 

This will return the item quantity, lot number, and expiration date in string format. Note that I could have specified a second parameterthe decimal separator characterfor the item quantity (ItemQty is a DECIMAL(9,2) field) as I did for expiration date (ExpDate is a Date field; therefore, I specified the date format ISO), but I chose not to do it because the second parameter is optional.

 

The VARCHAR function provides similar functionality, but it returns a varying-length string instead of a "traditional" fixed-length string. Note that varying-length strings are mostly used with language C APIs. VARCHAR provides a nice and easy way of converting a fixed to a varying-length string. The following statement returns the item Id field as a varying-length string:

 

SELECT            VARCHAR(ItemID)

FROM        InvMst

WHERE       ItemID = 'A123'

GROUP BY    ItemID

 

It's also important to mention that both CHAR and VARCHAR can be used to convert numeric and character data to the respective string representation.

 

Even though it has a somewhat similar name, VARCHAR_FORMAT is very different from VARCHAR. While VARCHAR can be used to convert several data types, VARCHAR_FORMAT can be used only to convert the timestamp or timestamp-compatible data types to the respective string representation. But there's a twist: VARCHAR_FORMAT's second parameter is the format string to apply to the timestamp. In a way, this provides functionality similar to RPG's %EDITW BIF. Here's an example that returns the current data and time in a user defined format:

 

SELECT            VARCHAR_FORMAT(NOW(),'YYYY-MM-DD HH24:MI:SS')

FROM        SYSIBM.SYSDUMMY1

 

This statement returns the current date and time, formatted in a more "human readable" way. I chose a simple format, but there are quite a lot of them available. Here are a few examples:

 

  • 'HH24-MI-SS'
  • 'HH24-MI-SS-NNNNNN'
  • 'YYYY-MM-DD'
  • 'YYYY-MM-DD-HH24-MI-SS'
  • 'YYYY-MM-DD-HH24-MI-SS-NNNNNN'

 

You can build your own formatting string, using the symbols explained in the VARCHAR_FORMAT section of the DB2 for i Reference manual. There, you'll find a rather large table detailing all the different possibilities.

 

The next article will continue to discuss string-related functions, which you can use to perform lowercase to uppercase conversions, among other interesting things. Until then, feel free to use the comments section below to agree, disagree, suggest topics for coming articles, or share your knowledge and experience with other readers. I'll be looking forward to hearing from you!

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

$0.00 Raised:
$

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: