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How can I create postgres db for Rails app properly but in psql, not via rake db:create?

I mean, one can always write CREATE DATABASE project_name, but I don't know what happens in that rake task under the hood. Maybe there are a lot of additional params.

Update

After first answer I decided to clarify: I know how to write and use migrations, they are awesome, but my question not about them. It's about rake db:create task and pg adapter.

In other words, I just want to know which command in psql is equal to rake db:create.

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    You can look in source code for rake db:create Commented Jun 13, 2015 at 22:53
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    If you don't trust the rake db:migrate, then why trust the Rails ActiveRecord component, or anything else? Part of the point of Rails is to abstract the data layer, so you're not writing db-specific sql code. This abstraction permits one to unplug and plugin a different database without changing model, view, or controller code. I understand the desire to be in complete control, but if you're writing psql code, you've just stepped back in time and circumvented the purpose of the MVC architecture. Commented Jun 13, 2015 at 22:58
  • I trust AR completely, and I use it's benefits: just yesterday I moved project from MySql to postgres, with ActiveRecord it is super easy. But when I set up server for that project I created postgres role for its DB (via psql) and I thought: maybe there is quick and safe way to create not only role but DB itself via psql, too? It is more curiosity than neccesarity. Commented Jun 14, 2015 at 9:16
  • @FlorentFerry thanks for the link. Quickly looked through code there, but it's too abstract. I just want to know which command in psql is equal to rake db:create command. Commented Jun 14, 2015 at 11:27

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If you select the db on pgadmin III it will show you the sql instructions with the local things to load. They are very importanst if you have full text index on. You must run them from the database postgres.

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Rails expects table names to match model names but be plural and snake_case. For example, a User model will store records in a users table and a BlogEntry model will store records in a blog_entries table.

Rails expects a table's primary key to be named id and it expects foreign keys to match model names but be snake_case and end with _id. For example, if BlogEntry belongs_to User, Rails will expect the blog_entries table to have a user_id column.

Join tables (such as used with many-to-many relations) are expected to be named with the two models' names in plural snake case and alphabetical order. For example, a join table describing a many-to-many relation between a User model and a Blog model would be expected to have the name blogs_users and have, at the least, the columns blog_id and user_id.

Those are the basics. Of course, all of this is configurable: For example, you can use the table_name class method to tell a model to use a table with a different name, and the relation methods (belongs_to, has_many, etc.) all take options letting you specify different names.

Apart from these naming conventions Rails doesn't require anything special from a database, as long as the correct credentials and configuration are specified in config/database.yml.

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Thank you for wide answer, but I know how migrations and associations work. But I do not know much about postgres.
You don't need to know much about Postgres beyond CREATE DATABASE and CREATE TABLE.

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