How Do I Access a Target Database with Your APEX App Using SQL

 In Oracle APEX, you may need to access an external or remote database to retrieve or update data. This can be done using Database Links, RESTful Web Services, or Oracle Autonomous Database's built-in connectivity features. Below are different ways to establish a secure connection and execute SQL queries against a target database.

1. Using a Database Link

A Database Link allows you to connect from your APEX database to a remote database and execute SQL queries.

Steps to Create and Use a Database Link

1. Create a Database Link in SQL Workshop (SQL Commands or SQL Scripts):

CREATE DATABASE LINK my_target_db

CONNECT TO remote_user IDENTIFIED BY 'password'

USING 'target_db_service_name';

Replace my_target_db with a unique name for the database link, remote_user with the target database username, password with the corresponding password, and target_db_service_name with the appropriate connection string.

2. Test the Connection by querying the remote database:

SELECT * FROM employees@my_target_db;

This retrieves the employees table from the remote database.

3. Use the Database Link in PL/SQL:

BEGIN

    FOR rec IN (SELECT first_name, last_name FROM employees@my_target_db) LOOP

        DBMS_OUTPUT.PUT_LINE(rec.first_name || ' ' || rec.last_name);

    END LOOP;

END;

This loop fetches and prints employee names from the remote database.

2. Using RESTful Web Services (For External Databases)

If you are working with a database that does not support database links, RESTful Web Services can be used to fetch data from a remote database.

Steps to Access Data Using RESTful Web Services

1. Enable ORDS (Oracle REST Data Services) in the target database.

2. Create a RESTful Web Service that exposes data.

3. Use APEX Web Source Modules to fetch the data:

• Navigate to Shared Components > Web Source Modules

• Create a new Web Source pointing to the REST API URL

• Use the data in Interactive Reports, Forms, or Charts

4. Query the Web Source from SQL or PL/SQL

SELECT * FROM apex_web_service.make_rest_request(

    p_url => 'https://api.targetdatabase.com/employees',

    p_http_method => 'GET'

);

This fetches JSON data from the external API.

3. Using Autonomous Database Features

If using Oracle Autonomous Database, Oracle-managed heterogeneous connectivity simplifies the process.

1. Use the DBMS_CLOUD Package to Query Remote Data

SELECT * FROM DBMS_CLOUD.list_objects(

    'my_credential',

    'https://my-target-database.com/employees'

);

This retrieves data directly from an external database or cloud-based storage.

2. Use a Wallet to Securely Connect to the Target Database

• Download the Wallet File from the target database.

• Upload it to APEX Instance Settings under Database Connectivity.

• Use the database link or RESTful API with secure authentication.

4. Best Practices for Secure Database Connectivity

• Always use SSL/TLS encryption for remote connections.

• Avoid storing credentials in queries—use APEX credentials instead.

• If using REST APIs, cache frequently accessed data to improve performance.

• Monitor database link usage to prevent performance bottlenecks.

By using database links, RESTful Web Services, or Autonomous Database features, you can securely access external databases from Oracle APEX and seamlessly integrate data into your applications.