重构SQL

我必须将我的Rails应用程序连接到Java应用程序上的远程数据库。

我有这样一个问题:

find_by_sql("select c_templateid, c_templateinfoid, c_startdate, c_enddate, c_active,
campaign, shortcode, prefix, c_descriptivename, c_description, c_templatename 
from (active_services aser join activity a on aser.c_primaryprefixid =
a.c_primaryprefixid ) join matrix_templateinfo using(c_templateinfoid) 
where campaign is not null)")

我需要将它重构为ar find()方法,因为我希望以后在上面添加复杂的:条件。我不想把它们转换成字符串来附加,然后用SQL方法查找。

find(:all, 
  :select => "c_templateid, c_templateinfoid, c_startdate, c_enddate, c_active,
  campaign, shortcode, prefix, c_descriptivename, c_description, c_templatename",
# :joins => WHAT I SHOULD DO HERE ?
  :conditions => "campaign is not null"
)