Azure Elastic Job Agent - Credentials

I want to refresh my tables in the same database with my queries using with Elastic Job Agent. I need to create credential first to connect database. How can I arrange the credentials in this case? Every documentation they have either 2 database or 2 server.

I found 2 sources but I couldn't understand the concept. Can you please explain it to me in a clear way?

Source 1 : Microsoft document

--Connect to the new job database specified when creating the Elastic Job agent

-- Create a database master key if one does not already exist, using your own password.  
CREATE MASTER KEY ENCRYPTION BY PASSWORD='<EnterStrongPasswordHere>';  
  
-- Create two database scoped credentials.  
-- The credential to connect to the Azure SQL logical server, to execute jobs
CREATE DATABASE SCOPED CREDENTIAL job_credential WITH IDENTITY = 'job_credential',
    SECRET = '<EnterStrongPasswordHere>';
GO
-- The credential to connect to the Azure SQL logical server, to refresh the database metadata in server
CREATE DATABASE SCOPED CREDENTIAL refresh_credential WITH IDENTITY = 'refresh_credential',
    SECRET = '<EnterStrongPasswordHere>';
GO

Source 2: link

    --In the master database
CREATE LOGIN mastercredential WITH PASSWORD='YourPassword1';

CREATE LOGIN jobcredential WITH PASSWORD='YourPassword2';

CREATE USER mastercredential FROM LOGIN mastercredential;

--In the job database
CREATE USER mastercredential FROM LOGIN mastercredential;

--In the target database
CREATE USER jobcredential FROM LOGIN jobcredential;

-- In the job database
CREATE MASTER KEY ENCRYPTION BY PASSWORD = 'YourPassword3';

CREATE DATABASE SCOPED CREDENTIAL mastercredential
WITH IDENTITY = 'mastercredential',
SECRET = 'YourPassword1';

CREATE DATABASE SCOPED CREDENTIAL jobcredential
WITH IDENTITY = 'jobcredential',
SECRET = 'YourPassword2';