Ruby Connecting to Mysql - MySql2

In the previous chapter, we introduced the use of Ruby DBI. This chapter focuses on a more efficient driver for connecting Ruby to Mysql, mysql2, which is currently recommended for this purpose.

To install the mysql2 driver:

gem install mysql2

You may need to use the --with-mysql-config configuration to specify the path to mysql_config, such as: --with-mysql-config=/some/random/path/bin/mysql_config.

Connection

The syntax for connecting to the database is as follows:

client = Mysql2::Client.new(:host => "localhost", :username => "root")

For more parameters, refer to http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/MysqlAdapter.html.

Query

results = client.query("SELECT * FROM users WHERE group='githubbers'")

Escaping Special Characters

escaped = client.escape("gi'thu\"bbe\0r's")
results = client.query("SELECT * FROM users WHERE group='#{escaped}'")

To count the number of results returned:

results.count

Iterating Through Results:

results.each do |row|
  # row is a hash
  # keys are database fields
  # values are corresponding data from MySQL
  puts row["id"] # row["id"].class == Fixnum
  if row["dne"]  # non-existent fields are nil
    puts row["dne"]
  end
end

Example

#!/usr/bin/ruby -w
require 'mysql2'

client = Mysql2::Client.new(
    :host     => '127.0.0.1', # Host
    :username => 'root',      # Username
    :password => '123456',    # Password
    :database => 'test',      # Database
    :encoding => 'utf8'       # Encoding
    )
results = client.query("SELECT VERSION()")
results.each do |row|
  puts row
end

The output of the above example is:

{"VERSION()"=>"5.6.21"}

Connection Options

Mysql2::Client.new(
  :host,
  :username,
  :password,
  :port,
  :database,
  :socket = '/path/to/mysql.sock',
  :flags = REMEMBER_OPTIONS | LONG_PASSWORD | LONG_FLAG | TRANSACTIONS | PROTOCOL_41 | SECURE_CONNECTION | MULTI_STATEMENTS,
  :encoding = 'utf8',
  :read_timeout = seconds,
  :write_timeout = seconds,
  :connect_timeout = seconds,
  :reconnect = true/false,
  :local_infile = true/false,
  :secure_auth = true/false,
  :default_file = '/path/to/my.cfg',
  :default_group = 'my.cfg section',
  :init_command => sql
  )

For more details, visit: http://www.rubydoc.info/gems/mysql2/0.2.3/frames.