Rails 3 execute custom sql query without a model - sql

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"}>, ...]

Answer 5

How about this :
#client = TinyTds::Client.new(
:adapter => 'mysql2',
:host => 'host',
:database => 'siteconfig_development',
:username => 'username',
:password => 'password'
sql = "SELECT * FROM users"
result = #client.execute(sql)
results.each do |row|
puts row[0]
end
You need to have TinyTds gem installed, since you didn't specify it in your question I didn't use Active Record