How to export a MySQL database to JSON?

Question

I am interested in exporting a subset of values from a MySQL database into a JSON-formatted file on disk.

I found a link that talks about a possible way to do this:

Answer 1

Another solution, if you are using Ruby, is to write a connection script to the database with ActiveRecord. You will need to install it first

gem install activerecord

# ruby ./export-mysql.rb
require 'rubygems'
require 'active_record'

ActiveRecord::Base.establish_connection(
  :adapter => "mysql",
  :database => "database_name",
  :username => "root",
  :password => "",
  :host => "localhost"
)

class Event < ActiveRecord::Base; end
class Person < ActiveRecord::Base; end

File.open("events.json", "w") { |f| f.write Event.all.to_json }
File.open("people.json", "w") { |f| f.write Person.all.to_json }

You can also add methods to the ActiveRecord classes if you want to manipulate data first or include or exclude certain columns.

Person.all.to_json(:only => [ :id, :name ])

With ActiveRecord you are not limited to JSON. You can just as easily export as XML or YAML

Person.all.to_xml
Person.all.to_yaml

You are not limited to MySQL. Any database supported by ActiveRecord (Postgres, SQLite3, Oracle... etc).

And it's worth mentioning you could open another handle to a database

require 'active_record'

ActiveRecord::Base.configurations["mysql"] = {
  :adapter  => 'mysql',
  :database => 'database_name',
  :username => 'root',
  :password => '',
  :host     => 'localhost'
}


ActiveRecord::Base.configurations["sqlite3"] = {
  :adapter  => 'sqlite3',
  :database => 'db/development.sqlite3'
}

class PersonMySQL < ActiveRecord::Base
  establish_connection "mysql"
end

class PersonSQLite < ActiveRecord::Base
  establish_connection "sqlite3"
end


PersonMySQL.all.each do |person|
    PersonSQLite.create(person.attributes.except("id"))
end

Here is a quick little blog post about it http://www.seanbehan.com/how-to-export-a-mysql-database-to-json-csv-and-xml-with-ruby-and-the-activerecord-gem