Database and check

Model basics is here.

Topics

About database

• Configuration file
• SQLite3
• MySQL
• Database setting detail

About operations

• See SQLite3
• Add database data from rails console
• Check in rails console

Configuration file

config/database.yml
Example(Mac OS X)

# SQLite version 3.x
#   gem install sqlite3
#
#   Ensure the SQLite 3 gem is defined in your Gemfile
#   gem 'sqlite3'
development:
  adapter: sqlite3
  database: db/development.sqlite3
  pool: 5
  timeout: 5000

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  adapter: sqlite3
  database: db/test.sqlite3
  pool: 5
  timeout: 5000

production:
  adapter: sqlite3
  database: db/production.sqlite3
  pool: 5
  timeout: 5000

SQLite3

You need gem

gem install sqlite3

MySQL

You need gem

gem install mysql2

Database setting detail

config/database.yml(Linux, Ubuntu)

development:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: mysqltest_development
  pool: 5
  username: root
  password:
  socket: /var/run/mysqld/mysqld.sock

See SQLite3

Use sqlite3 command(in application root)

sqlite3 db/development.sqlite3

After connecting, you can use SQL.

See table list

.tables

See table schema

.schema table_name

table_name is table name.

Exit

.exit

You can also use .quit to exit sqlite3

Add database data from rails console

rails console

You can see connector info

Loading development environment(Rails 4.0.2)

Create data example

Country.create(name:'Japan' population:10000000)

If you want to use new, some steps are required.

japan = Country.new
japan.name = 'Japan'
japan.population = 100000000
japan.new_record?     # check new record or not?
japan.save

Check in rails console

Check some data for testing(using rails console)

See first item

Country.first

See last item

Country.last

See all

Country.all

See class(database) definition

Country.first.class

See yaml style

puts Country.all.to_yaml

Get using each

Country.all.each do |country|
   puts country.name
end