RoR- Database setup& SQLite ... Migrations

*rails uses SQLite for database by default

*Built-in command-line DB viewer

*Self-contained,server-less,zero-configuration,transactional, relational SQL database.

Database Setup: config/database.yml

rails db - SQLite console mode

Turn headers on and column mode:

*.headers on

*mode columns

.exit 退出SQLite console

Migrations:

*Migration are just Ruby classes that get translated into DB speak

*Table in the DB keeps track of which migration was applied last

Ruby classes that extend ActiveRecord::Migration

File name need to start with a timestamp

apply all the migration:  rake db:migrate

Migration code maintains a table called schema_migrations table with one column called version.

Once the migration is applied - its version(timestamp) goes into the schema_migrations table.

database indenpence: different database adopter.

Exta Column Options:

null: true    null:false

limit: size

default: value

precision: value (total number of digits stored)

scale: value