Ruby on Rails: Is it better to validate in the model or the database?

Question

Is it generally better practice (and why) to validate attributes in the model or in the database definition?

For (a trivial) example:

In the user model:

validates_presence_of :name

versus in the migration:

t.string :name, :null => false 

On the one hand, including it in the database seems more of a guarantee against any type of bad data sneaking in. On the other hand, including it in the model makes things more transparent and easier to understand by grouping it in the code with the rest of the validations. I also considered doing both, but this seems both un-DRY and less maintainable.

Answer 1

I would highly recommend doing it in both places. Doing it in the model saves you a database query (possibly across the network) that will essentially error out, and doing it in the database guarantees data consistency.

Answer 2

It is good practice to do both. Model Validation is user friendly while database validation adds a last resort component which hardens your code and reveals missing validitions in your application logic.

Answer 3

It varies. I think that simple, data-related validation (such as string lengths, field constraints, etc...) should be done in the database. Any validation that is following some business rules should be done in the model.

Answer 4

Depends on your application design, If you have a small or medium size application you can either do it in both or just in model, But if you have a large application probably its service oriented or in layers then have basic validation i.e mandatory/nullable, min/max length etc in Database and more strict i.e patters or business rules in model.

Answer 5

And also

validates_presence_of :name

not the same to

t.string :name, :null => false 

If you just set NOT NULL column in your DB you still can insert blank value (""). If you're using model validates_presence_of - you can't.