IBI WebFOCUS - Difference between DEFINE and COMPUTE

In our day to day coding in WebFOCUS we would have used DEFINE and COMPUTE many a times. Even if you go for an interview this is the most common question (More than 90%). Surprising fact is there are many who cannot answer this question properly.

 Answering this question doesn't guaranty you the job but it is expected from a WebFOCUS developer to know the difference. First of all what is DEFINE and COMPUTE in WeBFOCUS term?

 The Answer is simple. Both does create virtual fields. They are used in WebFOCUS to perform calculated fields. Now when both does calculation, why do we have 2 options to do that?

 There are few differences listed below:
1) Calculation using DEFINE is on row by row basis meeting the selection criteria and Calculation using COMPUTE is done when all aggregation and sorting is done. For example- if the database has 100000 records for sales transaction and we want to aggregate it by 4 Regions. In case of DEFINE the calculation will happen 100000 times however in case of COMPUTE the calculation will happen only 4 times.
Now the question comes to our mind is how to choose from DEFINE and COMPUTE. Well! the answer depends on the requirement. 
a) If you are able to get the same result in both the cases, it is always preferred to use COMPUTE since performing computation 4 times is always better than doing it 100000 times.
b) If you are printing data at TABLE FILE level, then both will report same output and efficiency will also remain same.
c) If you need to filter on COMPUTE'd column, you need to use "WHERE TOTAL" with the column name however in case of DEFINE'd one you can simply use WHERE clause.

 Example:
Below is the detail of number of marks obtained by an student. Percentage column will be the calculated column based on general calculation of percentage of marks:



 If we need aggregated Marks and Percentage for the Student, the percentage would be (79+81+90 =250) in case of DEFINE, which is not correct. So be more careful in choosing from DEFINE and COMPUTE when you are doing division and multiplication in your calculation. 

 One more thing. It is always suggested to use least number of possible DEFINE'd and COMPUTE'd field to maintain the report performance.

Comments

Post a Comment

Popular posts from this blog

IBI WebFOCUS - Functions available and syntax to use

Using Functions Functions operate on one or more arguments and return a single value. The returned value can be stored in a field, assigned to a Dialogue Manager variable, used in a calculation or other processing, or used in a selection or validation test. Functions provide a convenient way to perform certain calculations and manipulations. There are two types of functions: Internal functions. Built into the WebFOCUS language, requiring no extra work to access or use. The following reporting and Maintain functions are internal functions. You can not replace any of these internal functions with your own functions of the same name. All other functions are external. ABS ASIS DMY, MDY, and YMD DECODE EDIT FIND LAST LOG LOOKUP MAX and MIN SQRT All Maintain-specific functions External functions. Stored in an external library that must be accessed. When invoking these functions, an argument specifying the output fie
Read more

IBI WebFOCUS - Testing and Debugging in WebFOCUS codes

You can debug a Web FOCUS application by querying your environment to display information such as file status, release, server information, and joins, as well as by identifying files you are using. Other debugging methods are available in Web FOCUS, including specialized Dialogue Manager Variables and traces performed from the Web Console. Debugging Your Application with Query Commands You can use query commands to display information about your metadata, data sources, language environment, Developer Studio, and Web FOCUS. This is useful for determining any aspects of your application that may be preventing the proper behavior of your application. You can query your environment with a query command executed in Developer Studio or Web FOCUS. The result of a query command is returned in your browser window or as a comment in the HTML file. Use the applicable Web browser functions to view the HTML comments (for example, View Source in Microsoft Internet Explorer). How to Issue
Read more

IBI WebFOCUS - Difference (Preference) between Join and Match:

For most of the reports in our WebFOCUS reporting world, we usually pull data from multiple tables and and generate the report. We all know that we can either Join Data Sources(JOIN) or Merge Data Sources(MATCH) to create report from multiple tables. Which one to choose from JOIN and MATCH? Now the question is what is the diffrence between the two and which one to choose from the 2 option. To explain this let's understand how does they process. JOIN: Basically JOIN is temporary, virtual connection between 2 or more physical or logical sources. Data in the first data source (host file) determines which records are retrieved from cross-reference file. When a record from the host file of a one-to-many join has no corresponding record(s) in the cross-reference file, the record is automatically excluded from the report output.  To control this, you can SET ALL to ON, in which case records from the host file, without corresponding records in the cross-reference file, will be disp
Read more