22
Mon, Jul
2 New Articles

TechTip: Use a Stored Procedure as Your Data Source in DB2 Web Query for i

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

Build queries with optional input parameters using existing business logic.

 

Do you need the ability to build queries with optional input parameters? Do you need your queries to use existing business logic? Did you know you can accomplish both goals by using a stored procedure as your data source in DB2 Web Query?

 

When we purchased DB2 Web Query, our shop needed to create new reports for a department that reports   accounting transactions to various state agencies and banking institutions. The business logic for the reports would be the same regardless of what state or bank was requesting the data, but the level of detail, the columns included, and the filtering could be different each run. Some states wanted details; some only summary. Some required information monthly; some quarterly. Some states wanted us to include beginning and ending balances along with the totals for the period being reported; others wanted information related only to period. The legacy reports that we were replacing were written in RPG and had no input parameters other than Month. They provided no ability to filter data. They had no ability to drop unwanted columns, nor did they let the users choose detail or summary output.

 

We knew that DB2 Web Query would give us what we needed. We also realized that we could "front end" multiple DB2 Web Queries with one stored procedure that could dynamically build an SQL SELECT statement that would allow us to provide optional input parameters. Additionally, by keeping the business logic in one stored procedure, we could eliminate duplicating/cloning it in multiple queries.

 

In this TechTip, I'll discuss writing a free-format SQLRPGLE program that receives parameters and dynamically builds a SELECT statement with a WHERE clause that includes only the optional parameters that the user populated. I'll discuss registering the SQLRPGLE program as a stored procedure and building a synonym over it. I'll show you how to build a summary query and a drill-down query that both use the same stored procedure's synonym.

Step 1: Creating Your Stored Procedure

If you are new to creating stored procedures in the System i, don't be intimidated. A stored procedure is only a program that you call from within SQL. You can write a stored procedure in languages you are already fluent in: RPG, CL, SQL, and others. Your stored procedure will select the records that match the selection criteria in your parameters. If applicable, your stored procedure can use existing business logic to segment your data. The stored procedure will then return your data as a result set to DB2 Web Query.

 

In our case, we have existing business logic that evaluates records in a large accounting transaction file. In addition to State, Location, and Contract#, each record carries a transaction code, period, and amount. The transaction code defines whether the transaction amount should be classified as Servicing$, Adjustment$, or Receipts$. Our stored procedure (STOREDPROC) uses that business logic to segment the transactions into the appropriate column. Additionally, STOREDPROC is using the parameters to filter the data in the file. The Start period and End period parameters are mandatory. The State, Location, and Contract# parameters are optional, and the SELECT statement built by STOREDPROC includes them in the WHERE clause only if they have a value.

 

Our parameters are defined in prototype STOREDPROC

 

  //- - - - - - - - - - - - - - - - - - - - - - - - - - - -

  // Input parms                                          

  //- - - - - - - - - - - - - - - - - - - - - - - - - - - -

                                                          

d inputparm       pr                  extpgm('STOREDPROC')

d  iState                        2                        

d  iLocation                     3                        

d  iContract                     9                        

d  isPeriod                      6                        

d  iePeriod                      6                        

                                                          

d inputparm       pi                                      

d  pState                        2                        

d  pLocation                     3                         

d  pContract                     9                        

d  psPeriod                      6                        

d  pePeriod                      6                        

 

The mainline code of STOREDPROC is very simple. Subroutine @build_select builds the dynamic SQL SELECT statement. Subroutine @open_cursor uses the SELECT statement to prepare and open the cursor for return to DB2 Web Query.

 

  //- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -      

  //  work fields                                                      

  //- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -      

d stm1            s           1000a                                    

d q               c                   ''''                              

  //- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -      

                                                                       

 /free                                                                 

                                                                        

  // build dynamic SQL select statement and include those               

  // parms supplied by the user                                        

  exsr     @build_select;                                               

                                                                       

  // use the select statement to open a cursor and send back result set

  exsr     @open_cursor;                                               

                                                                        

  // all done

  *inlr = *on; 

  return;   

                                                          

 

The first subroutine, @build_select illustrates two things:

  • The use of the existing business logic to segment the data into the appropriate columns
  • The use of the optional parameters in the WHERE clause

 

// ------------------------------------------------------            

begsr @build_select;                                                  

// ------------------------------------------------------            

                                                                     

 stm1 = 'SELECT +                                                    

   state, +                                                           

   location, +                                                       

   contract, +                                                       

   sum(case when (period < ' + pSperiod+ ') then amount else 0 end) +

     as begBal$, +                                                   

   sum(case when (tranCode = 20) +                                   

     and (period >= ' + pSperiod+ ') then amount else 0 end) +       

     as periodSer$, +                                                 

   sum(case when (tranCode in(0,6,9)) +                              

     and (period >= ' + pSperiod+ ') then amount else 0 end) +       

     as periodAdj$, +                                                

   sum(case when (tranCode in(2,3,7)) + 

     and (period >= ' + pSperiod+ ') then amount else 0 end) +  

     as periodRcpt$, +                                          

   sum(amount) +                                                

     as EndBal$ +                                                

                                                                

  FROM ACCTGFILE +                                              

  WHERE tranCode in (0,2,3,6,7,9,20) +                          

    and period <= ' + q + pEperiod+ q;                          

                                                                

  if pState > *blank;                                           

    stm1 = %trimr(stm1) + ' and state = ' + q + pState + q;     

  endif;                                                         

                                                                

  if pLocation > *blank;                                        

    stm1 = %trimr(stm1) + ' and location = ' + q + pLocation + q;

  endif;

        

  if pContract > *zeros;                                             

    stm1 =  %trimr(stm1) +  ' and contract = ' + q  + pContract + q; 

  endif;                                                             

                                                                     

  stm1 =  %trimr(stm1) +                                             

   ' GROUP BY state, location, contract +                             

     ORDER BY state, location, contract';                             

                                                                       

 endsr;                                                               

                                                                                                                                                  

The second subroutine, @open_cursor, uses the string just built to prepare, declare, open, and return a cursor as a result set to DB2 Web Query.

 

  // ------------------------------------------------------     

  begsr @open_cursor;                                           

  // ------------------------------------------------------     

                                                                

   exec sql prepare stmt from :stm1;                            

   exec sql declare C1 cursor with return to client for stmt;   

   exec sql open C1;                                            

   exec sql set result sets cursor C1;                          

                                                                

  endsr;                                                        

                                                                

After a successful compile of your program, you can register it as a stored procedure using the following SQL command:

 

CREATE PROCEDURE STOREDPROC

(IN STATE    CHAR(2) , 

 IN LOCATION CHAR(3) , 

 IN CONTRACT CHAR(9) , 

 IN SPERIOD  CHAR(6) , 

 IN EPERIOD  CHAR(6) ) 

 DYNAMIC RESULT SETS 1 

 LANGUAGE RPGLE        

 SPECIFIC       STOREDPROC

     DETERMINISTIC     

 READS SQL DATA        

 CALLED ON NULL INPUT  

 PARAMETER STYLE SQL   

 

Step 2: Testing Your Stored Procedure

You are now ready to test your stored procedure. The steps are simple: you simply use the Run SQL Scripts tool in iSeries Navigator to call your stored procedure with your parameters. An excellent TechTip by Kevin Forsythe details how to use iSeries Navigator to test a stored procedure.

 

Make sure to pass a value to your mandatory parameters. Play around with passing some of your optional parameters, and check the result set returned by your stored procedure. When you have verified that your SQL SELECT statement in your stored procedure is passing back correct results, you are ready to create a synonym.

 

Step 3: Creating a Synonym over Your Stored Procedure

These instructions assume you are familiar with creating a synonym over a table. To create a synonym over a stored procedure, select Stored Procedures in the "Restrict object type to" drop-down box as shown in Figure 1.

 

72409Corcoranfigure1_crop 

Figure 1: Choose the Stored Procedures option for Select Synonym Candidates. (Click images to enlarge.)

 

The Step 3 page of the Create Synonym pages will display the input parameters you defined in your stored procedure. When you click the Create Synonym button, your stored procedure will be called, and if it runs successfully and returns a result set, your synonym will be created and will include the parameters and all the fields in the result set. If your stored procedure includes any parameters that are mandatory for a successful run, then key in a valid value for those parameters as shown in Figure 2 before clicking Create Synonym.

 

072409Corcoranfigure 2_crop 

Figure 2: Complete the Create Synonym process.

 

Step 4: Using the Stored Procedure's Synonym in a Summary and Drill-Down Set of Web Queries

You can select the synonym over your stored procedure in DB2 Web Query and use it like any other synonym. The only difference you will notice is that your field list will contain separate segments for your parameters (segment INPUT) and the fields in your result set (segment ANSWERSET1). See Figure 3.

 

072409Corcoranfigure 3_crop 

Figure 3: This is the field list in Web Query for synonym STOREDPROC.

 

To filter the data returned by the stored procedure, include all your parameters in the Selection Criteria Window, as shown in Figure 4.

 

 072409Corcoranfigure 4_crop

 Figure 4: Include your parameters in the Selection Criteria window.

 

An example of the resulting simple summary query is shown in Figure 5. Note that we passed values into only the mandatory parameters.

 

072409Corcoranfigure 5_crop

Figure 5: Here are the results of a simple summary query.

 

You can turn this simple report into the parent in a drill-down set by selecting one of the fields and drilling down to a Web Query that uses the same STOREDPROC as its data source. You can, as appropriate, use fields from the answer set as the value for the parameters to be passed to the drill-down query. In this example, shown in Figure 6, we are allowing the user to drill down on the Location field. We are passing to the drill-down query the values for State and Location in the answer set row selected. The remaining parameters passed are identical to the parameters on the parent Query.

 

072409Corcoranfigure 6_crop 

Figure 6:  Change the parameters used by the parent query when it executes the drill-down.

 

I hope this simple example will inspire you to try this in your own shop. In future TechTips, I'll expand this example to include the addition of the input parameter values, user, and run date/time in the DB2 Web Query header and footer. I'll also show you a way get your stored procedure's synonym to work with the user's library list.

 

 

Anita Corcoran

Anita Corcoran, who has worked on IBM midrange systems since 1980, is a Senior Systems Analyst at StoneMor Partners L.P. in Levittown, Pennsylvania. She can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..

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: