ios – FIRDatabaseQuery：如何进行内连接

我正在尝试在FIR DatabaseQuery对象上进行内部联接.

下面是数据库结构.我有一些链接到评论后的帖子.我试图获取特定用户添加评论的所有帖子：

{
   "posts" : {
    "-KIycKhZU55dmKnHbbxv" : {
      "author" : "John Doe",
      "body" : "This is a post test",
      "title" : "test",
      "uid" : "SHaH36BLwgPvwgi9cDmRnsnONFB2"
    },
    "-KIyg_ks1O5QL4_4dfq_" : {
      "author" : "Jane Doe",
      "body" : "This is a post test",
      "title" : "test2",
      "uid" : "x5leSBGArnd10JilD9YDyNBNfZ03"
    },...
   }
  "post-comments" : {
    "-KIycKhZU55dmKnHbbxv" : {
      "-KIycMyL0Vy1BHVdI4zc" : {
        "author" : "toto",
        "text" : "test",
        "uid" : "SHaH36BLwgPvwgi9cDmRnsnONFB2"
      },
      "-KIyg_ks1O5QL4_4dfq_" : {
        "author" : "toto",
        "text" : "test",
        "uid" : "SHaH36BLwgPvwgi9cDmRnsnONFB2"
      }
    },...
 }

在SQL中,这将被翻译成类似于的内部联接查询：

选择*来自post post的内部联接后评论post-comments.uid =“user id”

有人知道如何在firebase中获得类似于内连接的东西吗？

非常感谢,
亚辛

您将需要使用嵌套的firebase调用.你可以找到一个 javascript example in this question,但你的swift代码应如下所示：

ref.child("posts").observeEventType(.ChildAdded, withBlock: { (snapshot) in
    if let postId = snapshot.key as! String {
      let commentsRef = ref.child("post-comments")  
      commentsRef.child(postId).queryOrderedByChild("uid").queryEqualToValue(userId).observeSingleEventOfType(.Value, withBlock: { (snapshot) in
            for child in snapshot.children.allObjects as [FDataSnapshot] {
               print(child.value)     
            }
        }) { (error) in
            print(error.localizedDescription)
        }
      }
})