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Virtually all Yii applications are built on top of a database, and though Yii is very flexible in how it addresses your DB, some design choices make things more convenient than others.

Relational databases do not support inheritance so if we need to represent it, we have to somehow store meta info while keeping performance by minimizing JOINs. One way to solve this problem is using single table inheritance. All fields for the whole class tree are stored in a single table. Class name is stored in the type field of the same table.

The customary configuration of a Yii application includes just a single database section in the protected/config/main.php file, but it's easy to extend this to support more than one, tying each Model to one of the databases.

To get null from database instead of empty strings you need to set up your DB connection as follows:

This is an incipient implementation of application-driven database with Yii.

What would you do if you want/need to have a different than the main database connection in an module's models?

This is a tutorial for how to auto set model values without any code.

Add these lines in /config/main.php

I like programing on my localhost, however it really bugged me to make changes to index.php & config files on my production server. After combining all available wiki articles on this topic and some trial and error this is what I use for my applications so I could just upload it to production server and it will work without any changes.

Suppose to have two models: Users and Emails. You do not want to store email in a Users model. And User can have 0 or many emails. This is the form generated to create a new user (just username).