带有ActiveRecord和Rails 3的复杂JOIN

微尘乙

我有以下型号：
class User  :memberships
! ~* S: r' h; |' `, y" Uend
class Group  :memberships
end
" d$ D. a: Y2 m! }: z5 L; _class Membership 我必须找到属于user是成员的组的所有帖子。我已经用这种方法做到了：
@post = Post
$ d, u, z0 |( p. G$ w  .joins(:group => {:memberships => :user})
  .where(:memberships => {:user_id => current_user.id})
但它会产生无效的SQL：
SELECT "posts".* FROM "posts"
INNER JOIN "groups" ON "groups"."id" = "posts"."group_id"
: s' [2 F" w9 y) X  x4 `. [INNER JOIN "memberships" ON "memberships"."group_id" = "groups"."id"
1 X9 F) W. K9 L3 MINNER JOIN "users" ON "users"."id" = "memberships"."user_id"
5 h: t1 N( z( a1 @WHERE "memberships"."user_id" = 1
3 H/ v  W5 q! B" W1 N% [3 D我想这样查询：
SELECT posts.* FROM posts
INNER JOIN memberships ON memberships.group_id = posts.group_id
$ y' C: S. t5 b% A0 T8 T2 OWHERE memberships.user_id = 1
* w  q# _& B2 x3 i% c. F( Y不使用原始SQL怎么办？
               
: H+ Z0 ?) i' J) ~3 |- _解决方案:
               
! @3 T# t+ W; M
+ m. U! L5 }" W% p
                像这样的事情应该为您工作，尽管它需要混入一些原始SQL
' ^2 |: i/ c0 s. QPost
  .joins("INNER JOIN memberships ON memberships.group_id = posts.group_id")
  .where(:memberships => {:user_id => current_user.id})