Oracle APEX表单中的字段条件渲染实现咨询：基于'arrear students'表存储值控制显示

Alright, let's figure out how to build that Oracle APEX form on your arrear students table where input fields only show up if their stored value is NULL. Here's a step-by-step breakdown that's easy to follow:

Start by using APEX's Form Wizard to create a standard form tied to the arrear students table. Add all the fields you need to the form—don't worry about hiding anything yet; we'll handle that next. Make sure your form has a primary key item (like P1_STUDENT_ID) to identify which record you're editing.

For every input field you want to control, you'll need to add a server-side condition that checks if the stored value is NULL. Here's how to do it for a single field:

• Open the Page Designer and locate the input field (e.g., P1_FEES_DUE) in the Rendering tab.
• In the Properties panel on the right, scroll down to the Server-side Condition section.
• Set the Condition Type to SQL Expression.
• Enter this expression (replace <YOUR_COLUMN> with the actual column name from your table):

  (:P1_STUDENT_ID IS NULL) OR (SELECT 1 FROM arrear_students WHERE student_id = :P1_STUDENT_ID AND <YOUR_COLUMN> IS NULL)
  

  The :P1_STUDENT_ID IS NULL part ensures all fields show up when you're creating a new record (since there's no stored value yet). If you don't want fields to show on new records unless specified, you can remove that part.
• Save your changes and repeat this for every field you need to control.

Pro Tip for Bulk Fields #

If you have a bunch of fields to set up, use APEX's Bulk Edit feature:

• Hold Ctrl/Cmd to select multiple fields in the Rendering tab.
• Right-click and choose Bulk Edit.
• In the bulk edit window, set the Server-side Condition Type and SQL Expression once, and it'll apply to all selected fields. Just remember to adjust the column name for each field if needed.

• Try editing an existing record where some fields have values and others are NULL—your form should only display the fields that are NULL in the database.
• Test creating a new record to make sure all fields show up (if you kept that part of the condition) or adjust as per your exact requirement.

内容的提问来源于stack exchange，提问作者Skydark