Oracle Database Tips by Donald Burleson

Updating the Database from APEX Form Checkboxes

The session state for a checkbox item is formatted as a colon delimited string.  In order to update the database with the checkbox data, it is necessary to destruct the colon delimited string into an array.  It can then be looped through the array and the data placed into a database table.

The code in file ch10_2.sql is stored in an On Submit - After Computations and Validations page process.

There is something very important to understand with checkboxes.  Figure 10.2 shows five checkboxes.  If the user selects three of the checkboxes and submits, the session state would look something like 2:3:1.  Assume the session state for the P2501_CLASS_ID page item was set to 5:2:3:1 during page rendering and the user un-selected the Calculus item.  Now, the problem is how to remove the data from the XR_STUDENT_CLASS table indicating the student has withdrawn from the Calculus class?  The common practice is to delete all data in the XR_STUDENT_CLASS table for the student and re-insert the data from the P2501_CLASS_ID session state.

Listing 10.2 shows a DELETE statement which deletes all the current data in the XR_STUDENT_CLASS table.  The session state for the P2501_CLASS_ID checkbox is then converted into an array.  At that point, the process loops through the array and inserts records to the XR_STUDENT_CLASS table indicating the class the student is enrolled in.  This will probably seem like an unnecessary task at first, but this is the usual method in APEX.

Working with Checkboxes in Reports and Tabular Forms

Working with checkboxes on a form is one thing, but working with checkboxes in reports or tabular forms is totally different.  How to add checkboxes to reports and tabular forms is the sort of question often asked on the Oracle HTLM DB forum.

Populating Checkboxes in a Report Region

The code used to populate the report in Figure 10.4 is shown in ch10_3.sql.  The key to populating a report with a checkbox is to use the htmldb_item.checkbox API function.  The parameters used are a subset of the available parameters, but an explanation of them is necessary for a full understanding of what is happening.  Table 10.1 explains some of the parameters for the htmldb_time.checkbox API function.

Running the SQL statement from ch10_3.sql in an SQL Command window will result in what is shown in Figure 10.5.  The htmldb_item.checkboxfunction returns the HTML syntax for an input of type checkbox.  Also, take note of the name.  It is set to f10 because the P_IDX parameter was set to ten.  The value of each of the checkboxes is determined from the CLASS_ID column.  Finally, all checkboxes will be displayed as checked.

Updating the Database from Report Checkboxes

Updating the database from checkboxes in a report is similar to that of checkboxes on a form.  A separate On Submit page process will be used to handle the data from the checkboxes.  Our example shows a report region.  However, when using a tabular form, it should be allowed to perform its database updates, and then run the process to handle the checkboxes.  Either way, a separate process will be created.

The code in file ch10_4.sql is stored in an On Submit - After Computations and Validations page process.  It will be executed when the page is submitted by pressing the Apply Changes button shown in Figure 10.2.

When the page is submitted, the values from the checkboxes are submitted in an array.  Referencing the array is done by using the htmldb_application package.  The g_f10 item is an array defined in the package.  As with the checkboxes in forms, the report checkboxes are only submitted in the g_f10 array.  Therefore, if there are four checkboxes checked, there will be four values in the array.  In the PL/SQL code in ch10_4.sql, the first step is to update the AVAILABLE_FLAG in all the records of the CLASS table.  Then the appropriate records are updated with a value of Y where the value in the g_f10 array item is equal to that of the CLASS_ID.

As I said in the beginning, "Checkboxes are rather tricky."  Using the examples described in the preceding pages, it should be possible to do most of what a developer will ever need to do in APEX in regards to checkboxes.

The above book excerpt is from:

Easy HTML-DB Oracle Application Express

Create Dynamic Web Pages with OAE

ISBN 0-9761573-1-4   

Michael Cunningham & Kent Crotty

http://www.rampant-books.com/book_2005_2_html_db.htm