Listing 13.1. Query used to create a new LOV for Course_ID.

select Course_ID
from Course
where
Department_ID = :Department.Department_ID
order by Course_ID

Figure 13.24.
Creating a new LOV
for Course_ID.

Looking at the object nodes with the Object Navigator, you'll notice that there are two new objects: an LOV named LOV15 and a record group named LOV15. Please realize that you might see different default names given to these objects. To change the name of the record group, select the record group with the mouse and left-click it once more. The name will become blue, and the pointer will become an insertion point. Name the record group COURSE_ID_RG, and name the LOV COURSE_ID_LOV as shown in Figure 13.25.

Figure 13.25.
Renaming the LOV
and record group.

You'll want to modify a property of COURSE_ID_LOV. To do this, select COURSE_ID_LOV and right-click Properties. Scroll down until you reach the Column Mapping property. Click the button labeled More at the top of the Properties window (see Figure 13.26).

Figure 13.26.
Modifying the
properties of an LOV.

The LOV Column Mapping window will appear. There are four fields in this window. The Column Names field identifies the columns that are returned by the record group's query. The Return Item field is used to specify the block item in which the current value in the Column Names field is to be deposited. The Display Width field indicates the width of the field as displayed in the LOV. Finally, the Column Title field holds the title that will be displayed when the LOV is invoked.

As displayed in Figure 13.27, enter Course_ID in the Return Item field; this will cause the Course_ID selected the user to be placed in the Course_ID item. Increase the Display Width to 55 points so that the LOV heading for Course_ID isn't truncated. Change the Column Title to Course ID. Click OK for these changes to take effect.

Figure 13.27.
Modifying the
Column Mapping
property of an LOV.

However, there are a few more steps that you need to perform before the LOV is actually used in the form.

1. Use the Object Navigator, and select the Course_ID item; right-click Properties.
2. Scroll down until you see a group of properties labeled Miscellaneous and select the LOV property.
3. Select COURSE_ID_LOV from the poplist at the top of the Properties window as shown in Figure 13.28.
4. Change the LOV for Validation property to True by clicking it; this will prevent a value from being entered into the field unless it exists in the LOV.

Let's test out the modified form.

1. Click on the green signal light from the vertical toolbar, or select File | Run from the menu.
2. When the runtime form is displayed, maximize both windows.
3. Execute a query by clicking twice on the Query button—once to enter query mode, and a second time to execute the query. You will see the first department appear in the Department block: Anthropology. However, there are no classes offered by this department.
4. Using the mouse, click on the first row in the Class block.
5. In Class_ID, enter 222333.

Figure 13.28.
Modifying the Course_IDitem
properties to use the
LOV.

6. Press Tab to navigate to Course_ID. You should see <List> at the bottom of the screen in the status line; this indicates that there is an LOV for Course_ID.
7. To display the LOV, press F9. You will see the LOV displayed in the upper-left corner of the screen (see Figure 13.29).

Figure 13.29.
Displaying the LOV
for Course_ID.

Scroll down to course 189 and press Enter; you will see 189 in the Course_ID item. If you enter a course that doesn't exist for this department, such as 1234, and press Tab to navigate to the next item, the form will display the LOV and also display a message in the message line stating FRM-40212: Invalid value for field COURSE_ID (see Figure 13.30).

Figure 13.30.
LOV enforces valid
values for
COURSE_ID.

Before you complete this lesson, save this form as Department_Class.fmb by selecting
File | Save as from the menu.

Summary

In this lesson, you learned the following:

• It is easy to construct master-detail forms with the Forms Designer.
• A master block is identified when the detail block is created.
• You use the Layout Editor to modify the form's appearance.
  

• You can modify the properties of several items at once by selecting them and, for example, changing their font.
• Using the Layout Editor, you can add graphical elements to a form by selecting tools from the vertical toolbar.
• When you create an LOV, you can automatically create the record group for the LOV by specifying the query for the record group.
• To use an LOV, the LOV property for an item must be set. If you want the LOV to validate user input in the item, you must set the LOV for Validation property to True.

What Comes Next?

On Day 14, "Developer/2000: Application Development with Oracle Forms," you learn how to construct a menu, add items to a block to display derived information, create form-level, block-level, and item-level triggers, and call a form from another form and pass a parameter to the invoked form.

Q&A

Q Can a master-detail form consist of more than one detail block?

A Yes. You simply create each detail block that you want and identify the master block in the Master/Detail tab.

Q Is it possible for several LOVs to reference the same record group?

A Yes. There is no restriction requiring each LOV to have its own record group.

Q Can a form have multiple windows and Canvas-Views?

A Yes, a single form can have multiple windows and Canvas-Views. However, as you will see in the next lesson, it usually makes more sense to create a multiple form application in which each form has a single Canvas-View and window.

Workshop

The purpose of the Workshop is to allow you to test your knowledge of the material discussed in the lesson. See if you can correctly answer the questions in the quiz and complete the exercises before you continue with tomorrow's lesson.