Rails 3在没有模型的情况下执行自定义的sql查询
我需要编写一个独立的ruby脚本来处理数据库。 我在rails 3中使用了下面给出的代码
@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 但得到错误： –
`<main>': undefined method `execute' for #<ActiveRecord::ConnectionAdapters::ConnectionPool:0x00000002867548> (NoMethodError)
我在这里错过了什么？
解
从denis-bu获得解决scheme后，我用下面的方式，也工作。
@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
也许试试这个：
ActiveRecord::Base.establish_connection(...) ActiveRecord::Base.connection.execute(...)
connection = ActiveRecord::Base.connection connection.execute("SQL query")
我build议使用ActiveRecord::Base.connection.exec_query而不是ActiveRecord::Base.connection.execute ，它返回一个ActiveRecord::Result （在rails 3.1+中可用），这有点容易处理。
然后，您可以通过各种方式（如.rows ， .each或.to_hash以各种方式访问它
从文档 ：
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
注意：从这里复制我的答案
你也可以使用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"}>, ...]
这个怎么样 ：
@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
你需要安装TinyTds gem，因为你没有在你的问题中指定它，我没有使用Active Record
