RoR- Database setup& SQLite ... Migrations
*rails uses SQLite for database by default
*Built-in command-line DB viewer
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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
