将三个单独的模型合并为一个结果

Question

我有一个包含三个孩子的模型Newsfeed，NewsfeedImage，NewsfeedText和NewsfeedLink。

新闻源

NewsfeedImage

NewsfeedLink

NewsfeedText

从三个子模型中可以看出，每个模型代表一种不同类型的新闻源对象。我的问题是，我如何select *来自Newsfeed并包含每个附属儿童模型？期望的输出（忽略JSON）：

[{
    "id": "1",
    "userId": "1",
    "commentCount": "0",
    "likeCount": "0",
    "updatedAt": "2015-12-13 12:12:32",
    "createdAt": "2015-12-13 12:12:32",
    "newsfeedId": "1",
    "model": "1",
    "imgUrl": "http://i.imgur.com/...",
    "title": "Has anyone..."
}, {
    "id": "1",
    "userId": "1",
    "commentCount": "0",
    "likeCount": "0",
    "updatedAt": "2015-12-13 12:12:32",
    "createdAt": "2015-12-13 12:12:32",
    "newsfeedId": "2",
    "model": "2",
    "linkShort": "http://goo.gl/...",
    "linkLong": "http://www....",
    "title": "Has anyone ...?"
}, {
    "id": "1",
    "userId": "1",
    "commentCount": "0",
    "likeCount": "0",
    "updatedAt": "2015-12-13 12:12:32",
    "createdAt": "2015-12-13 12:12:32",
    "newsfeedId": "3",
    "model": "3",
    "body": "How much ...?",
    "title": "Question ..."
}]

我最初尝试使用连接，但数据交叉不正确。感谢您的帮助，感谢您抽出宝贵的时间来查看我的问题。

Answer 1

SQL查询：

SELECT * FROM Newsfeed
LEFT JOIN (
    SELECT newsfeedId, model, imgUrl, 
        null AS linkShort, null AS linkLong, null AS body, 
        title
    FROM NewsfeedImage 
    WHERE NewsfeedImage.newsfeedid = Newsfeed.id

    UNION ALL 

    SELECT newsfeedId, model, null AS imgUrl, 
        linkShort, linkLong, null AS body, 
        title
    FROM NewsfeedLink 
    WHERE NewsfeedLink.newsfeedid = Newsfeed.id

    UNION ALL

    SELECT newsfeedId, model, null imgUrl, 
        null AS linkShort, null AS linkLong, body, 
        title
    FROM NewsfeedText 
    WHERE NewsfeedText.newsfeedid = Newsfeed.id

) t

并在程序脚本中删除null个字段。