1.What is the difference between Drilldown reprt and Interactive report?
2. Is there any similarity between Classical report and Drill down Report?

There is no difference between drill down and interactive report, they are the same.

With drilldown reporting, SAP provides you with an interactive information system to let you evaluate the data collected in your application. This information system is capable of analyzing all the data according to any of the characteristics that describe the data. You can also use any key figures you wish to categorize your data. You can display a number of objects for a given key figure, or a number of key figures for a given object. In addition, the system lets you carry out any number of variance analyses (such as plan/actual comparisons, fiscal year comparisons, comparisons of different objects, and so on).

You can produce both simple, data-directed lists (basic reports) and complex, formatted lists in drilldown reporting (form reports).

Drilldown report provides you with comfortable functions for navigating through your data. For example, you can jump to the next level of detail or the next report object on the same level, hide individual levels and switch between the detail and drilldown lists. It also provides a number of additional functions which let you process lists interactively (sorting, conditions, ranking lists, and so on). SAP Graphics, SAPmail and the Excel List Viewer are also integrated into drilldown reporting.

The drilldown functions are divided into three groups which differ in the number of functions available. That way each user can choose the functional level most suited for his requirements.

In addition to the online functions for displaying reports, drilldown reporting also provides functions which let you print reports. A number of formatting functions are available to let you determine the look of your printed reports (page breaks, headers and footers, underscores, and so on).

The menus and the functions available directly on the drilldown report make it easy to use the information system.

What is an Interactive Report?

An interactive report generally works in the following fashion:

1. Basic list is displayed.
2. User double clicks on any valid line
    or
    User selects a line and presses as button on the tool bar.
3. The corresponding event is triggered
4. Then in the code, the line on which action was done, is read.
5. Depending on the values in that selected line, a secondary list is displayed.
6. Steps from 2-5 are repeated till the end.

From the above explanation, I believe, its clear that, the 20th list, will essentially depend on the "selected line" of 19th list. According to your question, you want to move to 20th list directly, without "a prior list". May I know the exact requirement so that, an appropriate solution can be suggested? 

Again, your question was, how to move to 20th list directly on pressing of execute button. Its not possible to move to 20th list. You must cross over a basic list, before you can go to a different list level, using the code given by Pavan. 

What are Drilldown reports?

The lines of basic list of a drilldown report when clicked, will take the user to the corresponding (standard) object's display.

For eg: Suppose your report's primary component is purchase requisition, (assume you are printing PR details), and the basic list displays details of many PRs.

Eg: when clicked on a particular line of the PR basic list, it takes you to std t-code me53 (display of purchase requisition). This is the 'Drill-down' functionality.

For this, in the at-line selection of your program, as per the above ex: you'll set the parameter ID of PR number BAN (that you can get from Data element) in memory (using set parameter id) and then calling the corresponding transaction (usually skipping initial screen of the std t-code). 

Likewise, if it's Material Number (Matnr), you'll be displaying MM03 transaction w.r.t. the line's matnr.

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