Question

require 'rubygems'
require 'mysql'
db = Mysql.connect('localhost', 'root', '', 'mohit')
//db.rb:4: undefined method `connect' for Mysql:Class (NoMethodError)
//undefined method `real_connect' for Mysql:Class (NoMethodError)
db.query("CREATE TABLE people ( id integer primary key, name varchar(50), age integer)")
db.query("INSERT INTO people (name, age) VALUES('Chris', 25)")
begin
 query = db.query('SELECT * FROM people')
 puts "There were #{query.num_rows} rows returned"
  query.each_hash do |h| 
     puts h.inspect
end
rescue
 puts db.errno
 puts db.error 
end

error i am geting is:

    undefined method `connect' for Mysql:Class (NoMethodError)
                    OR 
   undefined method `real_connect' for Mysql:Class (NoMethodError)

EDIT
return value of Mysql.methods

      ["private_class_method", "inspect", "name", "tap", "clone", "public_methods", "object_id", "__send__", "method_defined?", "instance_variable_defined?", "equal?", "freeze", "extend", "send", "const_defined?", "methods", "ancestors", "module_eval", "instance_method", "hash", "autoload?", "dup", "to_enum", "instance_methods", "public_method_defined?", "instance_variables", "class_variable_defined?", "eql?", "constants", "id", "instance_eval", "singleton_methods", "module_exec", "const_missing", "taint", "instance_variable_get", "frozen?", "enum_for", "private_method_defined?", "public_instance_methods", "display", "instance_of?", "superclass", "method", "to_a", "included_modules", "const_get", "instance_exec", "type", "<", "protected_methods", "<=>", "class_eval", "==", "class_variables", ">", "===", "instance_variable_set", "protected_instance_methods", "protected_method_defined?", "respond_to?", "kind_of?", ">=", "public_class_method", "to_s", "<=", "const_set", "allocate", "class", "new", "private_methods", "=~", "tainted?", "__id__", "class_exec", "autoload", "untaint", "nil?", "private_instance_methods", "include?", "is_a?"]

return value of Mysql.methods(false)

is []… blank array

EDIT2

mysql.rb file

 # support multiple ruby version (fat binaries under windows)
 begin
  require 'mysql_api'
  rescue LoadError
   if RUBY_PLATFORM =~ /mingw|mswin/ then
RUBY_VERSION =~ /(\d+.\d+)/
require "#{$1}/mysql_api"
 end
 end

 # define version string to be used internally for the Gem by Hoe.
  class Mysql
    module GemVersion
     VERSION = '2.8.1'
  end
  end

Answer 1

I had this same problem and solved this way:

1. make sure you have installed only the gem ruby-mysql
   and not the gem mysql. For me, now:

   $ gem list –local | grep mysql

   ruby-mysql (2.9.2)

2. If that is not the case, uninstall

   $ sudo gem uninstall mysql

(I uninstalled every gem with mysql in its name)
and then reinstalled ruby-mysql.

In my case, because I have mysql installed in a usb disk
the installation command was:

sudo env ARCHFLAGS="-arch i386" gem install ruby-mysql   --  

--with-mysql-config=/Volumes/usb/opt/bin/osx/mysql/bin/mysql_config

--with-mysql-lib=/Volumes/usb/opt/bin/osx/mysql/lib/      

--with-mysql-dir=/Volumes/usb/opt/bin/osx/mysql

(and I was using the 32bits binary for MacOs, don’t know if that applies for you)

Finally, my ruby test program was

require 'rubygems'
require 'mysql' 


dbh = Mysql.real_connect('localhost', 'root', 'your password', 'TEST')


res =  dbh.query("select * from Persons;");

puts res.class

res.each do |row|
    puts row.join(" ")
end