How to Implement a Delete Validation in PL/SQL with Oracle Apex скачать в хорошем качестве

How to Implement a Delete Validation in PL/SQL with Oracle Apex

Learn how to set up a `Delete Validation` in PL/SQL for Oracle Apex, ensuring proper data integrity in linked tables. --- This video is based on the question https://stackoverflow.com/q/68096826/ asked by the user 'testFreak' ( https://stackoverflow.com/u/16296618/ ) and on the answer https://stackoverflow.com/a/68097261/ provided by the user 'Littlefoot' ( https://stackoverflow.com/u/9097906/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: PL/SQL with Oracle Apex - Delete Validation Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l... The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- Implementing Delete Validation in PL/SQL with Oracle Apex When working with databases, maintaining data integrity is crucial, especially when handling related tables. In this guide, we'll explore a common scenario where you need to ensure that a record can be deleted from a table only if it's not referenced by another table. We'll be using Oracle Apex and PL/SQL to implement this logic effectively. Let's dive into the specifics! Problem Overview Imagine you have two tables: TEST_ENTRIES and TEST_CATEGORIES. The goal is to allow the deletion of records from TEST_CATEGORIES only if there are no corresponding entries in the TEST_ENTRIES table. If an attempt is made to delete a category still being used, the process should raise an error. Here's a brief overview of our tables: TEST_ENTRIES IDNAMECAT_ID1Desk12Arm chair13Other business stuff2TEST_CATEGORIES IDNAMEVISIBLE1Furniture12Consumables13Delete Me1Solution Approach To implement the delete validation, we can utilize two main approaches: Using Foreign Key Constraints: This is the most straightforward and effective way to enforce referential integrity. With foreign key constraints, the database handles the restrictions for you. Using Custom PL/SQL Code: If you prefer not to use constraints, you can write custom PL/SQL code to check for dependencies before allowing a deletion. Let's explore these methods further. Method 1: Using Foreign Key Constraints The preferred method is to establish a foreign key relationship between the two tables. Here’s how you can implement this: Add a Primary Key to the TEST_CATEGORIES table: [[See Video to Reveal this Text or Code Snippet]] Add a Foreign Key in the TEST_ENTRIES table to reference the TEST_CATEGORIES table: [[See Video to Reveal this Text or Code Snippet]] Testing the Foreign Key Constraint Now, let’s see how this works in practice: Attempting to delete a category that is being referenced (e.g., ID = 1) will result in an error: [[See Video to Reveal this Text or Code Snippet]] On the other hand, deleting a category that is not referenced (e.g., ID = 3) will succeed: [[See Video to Reveal this Text or Code Snippet]] Method 2: Custom PL/SQL Code If you opt for a custom solution, here's how you can set it up using PL/SQL: Declare and Initialize Variables: [[See Video to Reveal this Text or Code Snippet]] Conditional Deletion: [[See Video to Reveal this Text or Code Snippet]] Testing the Custom PL/SQL Code You can run the PL/SQL block and test it using different category IDs to see if it correctly handles both scenarios: For ID = 1, it raises an error, indicating child records exist. For ID = 3, it successfully deletes the record. Conclusion Managing data integrity with delete validations is critical in any relational database. Both methods discussed here, foreign key constraints and custom PL/SQL logic, are effective; however, using foreign keys is generally the best practice due to its simplicity and efficiency. Implementing these practices in your Oracle Apex applications will help keep your data accurate and reliable. If you have any questions or need further assistance with your Oracle Apex development, feel free to reach out!