ERROR 1227 (42000) at line 2: Access denied; you need (at least one of) the RDSADMIN USER privilege(s) for this operation

The error you're encountering is related to recent changes in Amazon RDS for MySQL's privilege model, specifically introduced in version 8.0.36 and later. This change affects how database users and privileges are managed.

In the latest versions of RDS for MySQL (8.0.36 and higher), direct modifications to the mysql database, including creating databases through methods that might have worked in earlier versions, are no longer allowed. Instead, you need to use proper MySQL account-management statements and ensure you have the correct privileges.

To resolve this issue, you should:

1. Ensure that the user account you're using to connect has the necessary privileges. In RDS for MySQL 8.0.36 and later, there's a new role called rds_superuser_role which has extensive privileges, including the ability to create databases.

2. If you're not using the primary administrative user (which should have the rds_superuser_role by default), you may need to grant the necessary privileges to your user. This can typically be done by an administrator using statements like GRANT CREATE ON *.* TO 'your_user'@'%';

3. If you're using the Entity Framework to create the database, ensure that the connection string or configuration you're using includes a user with sufficient privileges.

4. Consider using the rds_superuser_role if you need extensive privileges. This role can be granted to users by the primary administrative user.

5. If you're migrating from an older version, review your application code and database creation scripts to ensure they align with the new privilege model. You may need to update your code to use proper MySQL account-management statements instead of direct table modifications.

If you continue to face issues, you might want to consult with your database administrator to ensure the correct roles and privileges are set up for your specific use case in this new version of RDS for MySQL.

Remember, these changes were implemented to enhance security and align more closely with MySQL's privilege model, so adapting to these new practices is important for maintaining a secure and well-managed database environment.
Sources
Role-based privilege model for RDS for MySQL - Amazon Relational Database Service
Amazon RDS for MySQL supports rds_superuser_role for easier implementation of role based privileges