为一本书选择不同的作者 [英] SELECT distinct authors for a book

问题描述

我有以下输入:

{"_id": "series/cogtech/BertonKHS06","type": "Article", "title": "Speech Recognition.", "pages": {"start": 85, "end": 107}, "year": 2006, "booktitle": "SmartKom", "url": "db/series/cogtech/54023732.html#BertonKHS06", "authors": ["Andr? Berton","Alfred Kaltenmeier","Udo Haiber","Olaf Schreiner"]}

我想把所有的作者和他们的书分开，我试过这个查询:

I want to get all the authors separetly with their books, I tried this query :

db.publis.find({}, {authors:1, title:2, _id:0})

我的预期输出:

Book                Author
Speech Recognition  Andr? Berton
Speech Recognition  Alfred Kaltenmeier
Speech Recognition  Udo Haiber
Speech Recognition  Olaf Schreiner

推荐答案

Demo - https://mongoplayground.net/p/86ZQkXfN4BW

使用 $unwind

从输入文档中解构一个数组字段，为每个元素输出一个文档.每个输出文档都是输入文档，其中数组字段的值被元素替换.

Deconstructs an array field from the input documents to output a document for each element. Each output document is the input document with the value of the array field replaced by the element.

db.collection.aggregate([
  { $unwind: "$authors" }, // break into individual documents
  { $project: { _id: 0, book: "$title", author: "$authors" } }
])

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