闲来无事，结合以前的代码，总结了ruby on rails的查询方法，方便自己以后查看，也方便后来人，如下，欢迎批评指正

1::simpleDB

	modules = find(:all, :conditions => ["site_id != '' and next_crawl < ? and next_crawl is not null and next_crawl != 'nil' and active='#{active}' and (in_queue is null or in_queue='nil' or in_queue='false')", Time.now],:order=>"next_crawl")

	modules = Module.find(:all, :conditions => [" next_snapshot is not null and next_snapshot!='nil' and next_snapshot < ? and priority= ? and ready_for_queue = ? and uri not like 'http://weibo.com%'", Time.now, priority,true], :order=>"next_snapshot",:limit => limit)

	modules = Module.select(:all, :conditions => ["date > ?", "#{(current-20.day).strftime('%Y-%m-%d')}"], :order => 'date desc')

	modules = Module.find(post_id,:params => {:topic_id => topic_id})

2::Mysql

   Mysql使用find 进行查询

	module = Module.find("id")	Mysql默认 使用id 查询，直接find 即可

	modules = Module.find(:all, :conditions=>['brand_id = ? and charged >?',@brand_id, 1.months.ago]).uniq 根据条件 查询所有，去重复

	module = Module.find(:first,:conditions=>["member_id = ? and id = ?",session[:user_id],params[:job_id]])

	module = Module.find(:all,:conditions=>["id in (?)",job_ids])  in  job_ids 查询

	module = Module.find(:all, :conditions=>['col_name = ?',col_val], :order=>"created_at") 按照某个字段order

	Module.find(:all, :conditions => ['member_id = ?', @member.id]).map{|view| view.ft_id} 返回数据，值为ft_id的值

	modules = Module.find(:all, :limit => limit_no, :where => ["id = '#{id}' and date <= '#{date}'"], :order => [:created_at, :desc]) 排序 等等

	modules = Module.find(:all, :conditions=>['updated_at > ?', Time.now-20.minute],:order => 'id desc')

	modules = Module.find(:all,  :joins => [:join_col], :conditions =>['m_id = ?',m_id] )

	modules = Module.find(:all,:conditions=>["date > ? and site = 'http://s.weibo.com' and keyword != ''",total_day.day.ago],:order=>["keyword asc","date desc"])

	MemberSite.find(:all,:conditions=>["member_id = ?", @member.id]).group_by{|ms| ms.m_id}  内置方法之排序：group_by() 按照m_id 排序

	Module.find(:first, :conditions=>['survey_id = ? and name = ?', survey_id, 'STORY'], :select=>'question_id') 什么意思

	module = Module.find(:first, :order => "create_date, attending DESC")

   Mysql使用类似于jdbc的查询

	results = ActiveRecord::Base.connection_pool.with_connection do |connection|

	  	id = connection.quote(cuser_id)

			start_at = Date.parse(start_time).to_time.to_i * 1000

			end_at = Date.parse(end_time).to_time.end_of_day.to_i * 1000

			sql = " select count(*) as num from user_follower where cuser_id = #{id} and user_verified_type != -1 and followed_at >= #{start_at} and followed_at <= #{end_at} "

			connection.execute(sql)

		end

	result = ActiveRecord::Base.connection_pool.with_connection do |connection|

		      sql = "select count(user_id) as user_id_count from user_follower where cuser_id = '#{cuser_id}'"

		      connection.execute(sql)

		 end

		 @saved_followers_count = result.first[0] || 0

	results = ActiveRecord::Base.connection_pool.with_connection do |connection|

			id = connection.quote(cuser_id)

			sql = " select year, month, day, post_type, count(*) as num , group_concat(concat(post_id,':',topic_id) SEPARATOR ',' ) as ids "+

				" from posts_group_by_type_date_time where cuser_id = #{id} and " + generate_date_sql(startTime, endTime) + " group by year,month,day,post_type "

			connection.execute(sql)

		end

		把结果当做array返回 to_a

		if(results.count == 0)

			return []

		else

			return results.to_a

		end

    mysql 使用where查询

	Scope.where({:col => "XXX"}) 最简单的where查询

	@industries = Scope.where({:module_type => "industry"}).map{|scope| scope.scope} 上面有介绍

	@scope = Scope.where({:scope => params["scope"]}).first  返回第一个值

	Threads.where("scope = ? and period = ?", m.id, period).count 根据条件查询，然后count

	Analytics.where({:scope => m.id,:topic => 'all', :site_id=>'all',  :date => start_time...end_time}).sum("posts") 另外一种赋值方式

	Threads.where("scope = ? and topic like ? and period = ?", scope, "%#{topic}%", period).limit(50)  limit查询