做一个一次性查询到不同的数据库和表 [英] Make a one-off query to a different database and table

问题描述

我有一个词preSS博客（AT /博客完全分开）sellotaped一个侧面的滑轨应用程序。

I have a rails app with a wordpress blog sellotaped on the side (totally separately at /blog).

客户想的要在铁轨上的应用程序的主网页的最新博客文章，所以我需要做一个一次性的MySQL查询到字处理preSS数据库。我怎么会去在Rails应用程序这样做。该字处理preSS距离铁轨完全sperate在数据库方面。

The client want's to the latest blog post on the main homepage of the rails app, so I need to do a one-off mysql query to the word-press database. How would I go about doing this in the rails app. The word-press is completely sperate from rails in terms of database.

干杯。

推荐答案

假设它是访问使用相同的数据库凭据和相同的MySQL服务器上，最简单的方法是将运行一个查询指定的数据库和表从查询条款，因为这样：

Assuming it is accessible using the same database credentials and on the same MySQL server, the easiest way would be to run a query specifying the database and table in the FROM clause of the query, as such:

ActiveRecord::Base.connection.select_one(
    "SELECT * FROM blog_database.posts ORDER BY created_at DESC LIMIT 1")

select_one 将返回列的哈希值。有关方法的详细信息可以在连接物体上使用，请参阅<一href="http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/DatabaseStatements.html">this文档。

select_one will return a hash of columns to values. For more information on methods you can use on the connection object, see this documentation.

第二个选项是创建的ActiveRecord的子类，并调用 establish_connection ：

The second option is to create a subclass of ActiveRecord and call establish_connection:

class Blog < ActiveRecord::Base
  establish_connection :blog

  def self.most_recent_post
    connection.select_one("SELECT * FROM posts ...")
  end
end

您还需要在你的的database.yml 文件中的博客数据库条目。请参阅<一href="http://api.rubyonrails.org/classes/ActiveRecord/Base.html#method-c-establish_connection">establish_connection有关详细信息，但不幸的是使用它以这种方式真的只有通过查看源$ C ​​$下 establish_connection 众所周知的。

You will also need to make a blog database entry in your database.yml file. See establish_connection for more details, although unfortunately using it in this way is really only known by looking at the source code for establish_connection.

然后就可以使用查询博客数据库连接，如下所示：

Then you can use the blog database connection in queries, like so:

Blog.connection.select_one("SELECT * FROM posts ...")

什么是好的，这样做是这样，现在是你有一个很好的地方定义一个方法（在博客类，作为一个类的方法）来获取数据，我已经在上面做了。

What is nice about doing it this way is now you have a nice place to define a method (in the Blog class, as a class method) to fetch the data, as I have done above.

这两种策略，应该可以正常使用Rails x或3 x。

Both these strategies should work fine with Rails 2.x or 3.x.

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