Rails 3 execute custom sql query without a model

Question

I need to write a standalone ruby script that is supposed to deal with database. I used code given below in rails 3

@connection = ActiveRecord::Base.establish_connection(
:adapter => "mysql2",
:host => "localhost",
:database => "siteconfig_development",
:username => "root",
:password => "root123"
)

results = @connection.execute("select * from users")
results.each do |row|
puts row[0]
end

but getting error:-

`<main>': undefined method `execute' for #<ActiveRecord::ConnectionAdapters::ConnectionPool:0x00000002867548> (NoMethodError)

what i am missing here?

SOLUTION

After getting solution from denis-bu i used it following way and that worked too.

@connection = ActiveRecord::Base.establish_connection(
            :adapter => "mysql2",
            :host => "localhost",
            :database => "siteconfig_development",
            :username => "root",
            :password => "root123"
)

sql = "SELECT * from users"
@result = @connection.connection.execute(sql);
@result.each(:as => :hash) do |row| 
   puts row["email"] 
end

Answer 1

Maybe try this:

ActiveRecord::Base.establish_connection(...)
ActiveRecord::Base.connection.execute(...)

Answer 2

connection = ActiveRecord::Base.connection
connection.execute("SQL query") 

Answer 3

I'd recommend using ActiveRecord::Base.connection.exec_query instead of ActiveRecord::Base.connection.execute which returns a ActiveRecord::Result (available in rails 3.1+) which is a bit easier to work with.

Then you can access it in various the result in various ways like .rows, .each, or .to_hash

From the docs:

result = ActiveRecord::Base.connection.exec_query('SELECT id, title, body FROM posts')
result # => #<ActiveRecord::Result:0xdeadbeef>


# Get the column names of the result:
result.columns
# => ["id", "title", "body"]

# Get the record values of the result:
result.rows
# => [[1, "title_1", "body_1"],
      [2, "title_2", "body_2"],
      ...
     ]

# Get an array of hashes representing the result (column => value):
result.to_hash
# => [{"id" => 1, "title" => "title_1", "body" => "body_1"},
      {"id" => 2, "title" => "title_2", "body" => "body_2"},
      ...
     ]

# ActiveRecord::Result also includes Enumerable.
result.each do |row|
  puts row['title'] + " " + row['body']
end

note: copied my answer from here

Answer 4

You could also use find_by_sql

# A simple SQL query spanning multiple tables
Post.find_by_sql "SELECT p.title, c.author FROM posts p, comments c WHERE p.id = c.post_id"
> [#<Post:0x36bff9c @attributes={"title"=>"Ruby Meetup", "first_name"=>"Quentin"}>, ...]