Neo4j嵌套查询
问题描述：
我正在使用此密码来检索一组库的嵌套数据，每个库都有0-X数量的书，每本书有0-X数量的作者。 Cypher支架看起来是这样的：Neo4j嵌套查询
MATCH (library:Library)--(book:Book)--(author:Author)
WITH library, book, {name: author.name} AS nest_author
WITH library, {name: book.name, authors: collect(nest_author)} AS nest_book
WITH {name: library.name, books: collect(nest_book)} AS nest_library
RETURN {library_data: collect(nest_library)}
这个暗号唯一的问题是，只有当库有一本书，一本书有一个作者的作品。我想下面的查询，但结构会丢失，并在所有的书所有作者出现，所有的书出现在所有的图书馆：
MATCH (library:Library),(book:Book),(author:Author)
OPTIONAL MATCH (library)--(book)
OPTIONAL MATCH (book)--(author)
WITH library, book, {name: author.name} AS nest_author
WITH library, {name: book.name, authors: collect(nest_author)} AS nest_book
WITH {name: library.name, books: collect(nest_book)} AS nest_library
RETURN {library_data: collect(nest_library)}
如何将我写的第一个查询，这样的关系是可选当图书馆没有任何书籍或图书不包含作者时，收集只是返回一个空列表？
答
在您的第二个查询中，您正在创建交叉产品行为。
主要基于以下Neo4j的控制台例如：http://console.neo4j.org/r/l1cpwz
这个查询做的伎俩：
MATCH (n:Library)
OPTIONAL MATCH (n)--(book:Book)
OPTIONAL MATCH (book)--(author:Author)
RETURN n.name, collect({ book: book.title, author: author.lastname })
的例子结果如下：
n.name collect({ book: book.title, author: author.lastname })
aspernatur [ {book:"Eligendi fuga est harum est nobis nam id.", author:null}, {book:"Numquam animi ex alias rerum quas.", author:null}]
consectetur [ {book:"Vel nostrum modi officia.", author:null}, {book:"Dolorum dolor optio aut ipsum.", author:null}, {book:"Iste sit quo reprehenderit dolores neque.", author:null}]
corrupti [ {book:"Minus sit sed quia tempora quaerat.", author:null}]
deserunt [ {book:"Temporibus impedit quod aut vel et.", author:null}, {book:"Praesentium perspiciatis blanditiis et omnis suscipit nostrum repudiandae.", author:null}]
labore [ {book:"Non quis maxime doloremque et.", author:null}, {book:"Eos voluptatem voluptatibus mollitia exercitationem nobis.", author:null}, {book:"Vel voluptatem quae libero non est eaque.", author:null}, {book:"Atque velit accusantium perspiciatis assumenda voluptas ea corporis.", author:null}]
nihil [ {book:"Deleniti illo earum eaque sapiente perspiciatis omnis quia.", author:null}, {book:"Est eum enim quo suscipit et molestias.", author:null}, {book:"Consequuntur nam temporibus explicabo quia ipsum.", author:null}, {book:"Facilis ratione illum ipsum sed cum ut.", author:null}, {book:"Est eos quis suscipit ratione alias necessitatibus asperiores sunt.", author:null}, {book:"Odit voluptatem est reiciendis quod tempora.", author:null}]
officiis [ {book:"Ad libero porro quibusdam voluptatum.", author:null}, {book:"Numquam omnis ut unde sequi sint enim.", author:null}]
omnis [ {book:"Qui laboriosam alias repellendus quibusdam incidunt et.", author:null}, {book:"Eos officia vitae consequatur qui.", author:null}, {book:"Explicabo nemo eos maxime.", author:null}, {book:"Dolores voluptatum et similique natus dolore fuga perferendis molestiae.", author:null}, {book:"Quidem aut ut ut quas veritatis.", author:null}, {book:"In in quos et aspernatur dolores.", author:null}, {book:"Alias sed quasi explicabo possimus veniam temporibus.", author:null}, {book:"Omnis dolor eum molestiae veritatis.", author:null}]
tempore [ {book:null, author:null}]