Post < ActiveRecord::Base
belongs_to :author
has_many :comments, :order => 'created_on DESC'
end
如果我们遍历所有post访问作者和评论属性我们使用个Sql查询来返回posts表中多条记录并且对于每条post记录都要执行次Sql来访问authors表和comments表总共是2n+1次
for post in Post.find(:all)
puts "Post: #{post.title}"
puts "Written by: #{post.author.name}"
puts "Last comment _disibledevent=> [:author, :comment])
# ...
end
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