Ruby - ActiveRecord::ConnectionNotEstablished

Question

I am rather new to Ruby and have been following along with the book \"Ruby On Rails 3 Tutorial - Learn Ruby by Example - by Michael Hartl\". I am currently in Chapter 3 whic

Answer 1

In development environment, just run

bundle exec rake db:setup

In production environment, run

bundle exec RAILS_ENV=production rake db:setup

Answer 2

Below steps worked for me..

1. create blank development.sqlite3 file in db/ folder.

2. close current terminal and create fresh terminal

Then run rails server

Answer 3

bundle install
bundle update
rake db:setup
rake db:migrate
rake db:seed
# remember to restart the server
rails server

Answer 4

Using the latest sqlite3 + bundle update + bundle install worked for me. I believe the restriction to an older sqlite3 version per the walkthrough is likely messing things up. Here's my gemfile:

source 'https://rubygems.org'

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '4.0.0'



# Use sqlite3 as the database for Active Record
gem 'sqlite3'


# Use SCSS for stylesheets
gem 'sass-rails', '~> 4.0.0'

# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'

# Use CoffeeScript for .js.coffee assets and views
gem 'coffee-rails', '~> 4.0.0'

# See https://github.com/sstephenson/execjs#readme for more supported runtimes
# gem 'therubyracer', platforms: :ruby

# Use jquery as the JavaScript library
gem 'jquery-rails'

# Turbolinks makes following links in your web application faster. Read more:     https://github.com/rails/turbolinks
gem 'turbolinks'

# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 1.2'

group :doc do
  # bundle exec rake doc:rails generates the API under doc/api.
  gem 'sdoc', require: false
end

# Use ActiveModel has_secure_password
# gem 'bcrypt-ruby', '~> 3.0.0'

# Use unicorn as the app server
# gem 'unicorn'

# Use Capistrano for deployment
# gem 'capistrano', group: :development

# Use debugger
# gem 'debugger', group: [:development, :test]

Answer 5

Make sure that you have installed sqlite3 gem.

If so did you run the following commands,

rake db:create # to create database
rake db:migrate # to create tables based on your migration

If the above two works fine, your application should be able to connect to the database. Else please copy the trace application trace over here, that may help us to help you better.

Answer 6

I was migrating from a previous version of Rails. For me the fix was to add

require 'rails/all'

at the top of application.rb instead of the 5 separate requires I had.