【发布时间】：2021-05-30 13:56:50
【问题描述】：
我正在尝试查找至少有两位作者的书的 ISBN、书名和出版商 最多三位作者。 我是这样写的，但是在这个集合中 BOOK 是一个数组，那么书中的作者也是一个数组，所以对我来说有点复杂
db.Subject.aggregate([
{$unwind:{path:"$subject.book",preserveNullAndEmptyArrays: true}},
{$unwind:{path:"$subject.book.author",preserveNullAndEmptyArrays: true}},
{$group:{_id:{title:"$subject.book.bookTitle",
author:"$subject.book.author",publisher:"$subject.book.publisher",
Isbn:"$suject.book.ISBN"},counts:{$sum:1}}},
{$match:{$or:[{counts:{$eq:2}},{counts:{$eq:3}}]}}
])
但是作者和书的输出不正确我不知道我的代码的哪一部分有错误请帮助我谢谢 下面是主题集合的 json 文档
db.Subject.insert(
{
"_id":ObjectId(),
"subject": {
"subCode":"CSCI103",
"subTitle":"Algorithm and Problem Solving",
"credit":3,
"type":"Core",
"assessments": [
{ "assessNum": 1,
"weight":10,
"assessType":"Assignment",
"description":"Problem Solving and Invariant" },
{ "assessNum": 2,
"weight":10,
"assessType":"Assignment",
"description":"Assignment 1 - Sorting and Seaarching, Linked Lists, and Stack and Queues" },
{ "assessNum": 3,
"weight":10,
"assessType":"Assignment",
"description":"Assignment 2 - Recursion, Trees, and Algorithmic Strategies" },
{ "assessNum": 4,
"weight":10,
"assessType":"Test/Quiz",
"description":"Closed-book Class Test" },
{ "assessNum": 5,
"weight":60,
"assessType":"Examination",
"description": "Closed-book Final Examination" }
],
"book": [
{ "ISBN":"13:978-0-13-231681-1",
"bookType":"textbook",
"bookTitle":"Introduction to the Design and Analysis of Algorithms",
"edition":3,
"yearPub":2012,
"publisher":"Pearson",
"author": [ "Anany Levitin" ] },
{ "ISBN":"13:978-0-13-231681-1",
"bookType":"reference",
"edition":3,
"yearPub":2005,
"publisher":"Pearson",
"author": [ "B A Forouzan", "D S Malik", "M K Sen Thomson" ] }
]
}
}
)
db.Subject.insert(
{
"_id":ObjectId(),
"subject": {
"subCode":"CSCI114",
"subTitle":"Procedural Programming",
"credit":3,
"type":"Core",
"assessments": [
{ "assessNum": 1,
"weight":5,
"assessType":"Assignment",
"description":"Assignment 1 - Basic Concepts: Sequential Designs" },
{ "assignNum": 2,
"weight":5,
"assessType":"Assignment",
"description":"Assignment 2 - Control structures: Selection Designs" },
{ "assessNum": 3,
"weight":5,
"assessType":"Assignment",
"description":"Assignment 3 - Repetition Designs and Functions I" },
{ "assessNum": 4,
"weight":15,
"assessType":"Test/Quiz",
"description":"Closed-book Class Test" },
{ "assessNum": 5,
"weight": 10,
"assessType":"Test/Quiz",
"description":"Laboratory Test" },
{ "assessNum": 6,
"weight": 10,
"assessType":"Test/Quiz",
"description": "Closed-book Class Test" },
{ "assessNum": 7,
"weight":50,
"assessType":"Examination",
"description": "Closed-book Final Examination" }
],
"book": [
{ "ISBN":"13:978-1-133-52635-3",
"bookType":"reference",
"bookTitle":"C++ Programming - Program design including data structure",
"edition":6,
"yearPub":2013,
"publisher":"CENGAGE Learning",
"author": [ "Malik D S" ] },
{ "ISBN":"13:978-0-273-75983-6",
"bookType":"reference",
"bookTitle":"Starting Out With C++: From Control Structures through Objects",
"edition":7,
"yearPub":2012,
"publisher":"Addison-Wesley",
"author": [ "Tony Gaddis" ] },
]
}
}
)
db.Subject.insert(
{
"_id":ObjectId(),
"subject": {
"subCode":"CSCI124",
"subTitle":"Applied Programming",
"credit":3,
"type":"Core",
"prerequisite": ["csci114"],
"assessments": [
{ "assessNum": 1,
"weight":12,
"assessType":"Assignment",
"description":"Assignment 1 - Application on binary file processing" },
{ "assignNum": 2,
"weight":12,
"assessType":"Assignment",
"description":"Assignment 2 - Application on pointers" },
{ "assessNum": 3,
"weight":12,
"assessType":"Assignment",
"description":"Assignment 3 - Application on classes and objects and dynamic data structures" },
{ "assessNum": 4,
"weight":14,
"assessType":"Laboratory",
"description":"Laboraory/Implementation Tasks" },
{ "assessNum": 5,
"weight": 50,
"assessType":"Examination",
"description":"Closed-book Final Examination" }
],
"book": [
{ "ISBN":"10:1-4390-4023-0",
"bookType":"textbook",
"bookTitle":"Data Structures Using C++",
"edition":2,
"yearPub":2010,
"publisher":"CENGAGE Learning",
"author": [ "Malik D S" ] },
{ "ISBN":"13:978-1-133-52635-3",
"bookType":"reference",
"bookTitle":"C++ Programming - Program design including data structure",
"edition":6,
"yearPub":2013,
"publisher":"CENGAGE Learning",
"author": [ "Malik D S" ] },
{ "ISBN":"13:978-0-273-75983-6",
"bookType":"reference",
"bookTitle":"Starting Out With C++: From Control Structures through Objects",
"edition":7,
"yearPub":2012,
"publisher":"Addison-Wesley",
"author": [ "Tony Gaddis" ] }
]
}
}
)
db.Subject.insert(
{
"_id":ObjectId(),
"subject":{
"subCode":"CSCI235",
"subTitle":"Database Systems",
"credit":3,
"type":"Core",
"prerequisite": ["csci124","csci103"],
"assessments": [
{ "assessNum": 1,
"weight":10,
"assessType":"Assignment",
"description":"Assignment 1 - Normalization and Indexing" },
{ "assignNum": 2,
"weight":10,
"assessType":"Assignment",
"description":"Assignment 2 - PL/SQL programming and Concurrency Control" },
{ "assessNum": 3,
"weight":10,
"assessType":"Assignment",
"description":"Assignment 3 - JSON/BSON and MongoDB" },
{ "assessNum": 4,
"weight":10,
"assessType":"Laboratory",
"description":"Laboraory/Implementation Tasks" },
{ "assessNum": 5,
"weight": 60,
"assessType":"Examination",
"description":"Closed-book Final Examination" }
],
"book": [
{ "ISBN":"13:978-0-136-08620-8",
"bookType":"textbook",
"bookTitle":"Fundamentals of Database Systems",
"edition":6,
"yearPub":2010,
"publisher":"Addison-Wesley",
"author": [ "Ramez Elmasri", "Shamkant B Navathe" ] },
{ "ISBN":"0-07-246563-8",
"bookType":"reference",
"bookTitle":"Database Management Systems",
"edition":3,
"yearPub":2003,
"publisher":"McGraw-Hill",
"author": [ "Raghur Ramakrishnan", "Johannes Gehrke" ] } ]
}
}
)
db.Subject.insert(
{
"_id":ObjectId(),
"subject":{
"subCode":"CSCI203",
"subTitle":"Algorithm and Data Structures",
"credit":3,
"type":"Core",
"prerequisite": ["csci103"],
"assessments": [
{ "assessNum": 1,
"weight":10,
"assessType":"Assignment",
"description":"Assignment 1 - Mathematic Concepts and Algorithm Complexity" },
{ "assignNum": 2,
"weight":15,
"assessType":"Assignment",
"description":"Assignment 2 - Linear and Non-linear Data Structure" },
{ "assessNum": 3,
"weight":15,
"assessType":"Assignment",
"description":"Assignment 3 - Greedy Algorithm and Branch-and-Bound" },
{ "assessNum": 4,
"weight": 60,
"assessType":"Examination",
"description":"Closed-book Final Examination" }
],
"book": [
{ "ISBN":"13:978-0-13-231681-1",
"bookType":"textbook",
"bookTitle":"Introduction to the Design and Analysis of Algorithms",
"edition":3,
"yearPub":2012,
"publisher":"Pearson",
"author": [ "Levitin" ] },
{ "ISBN":"978-0-262-53305-8",
"bookType":"reference",
"bookTitle":"Introduction to Algorithms",
"edition":3,
"yearPub":2013,
"publisher":"The MIT Press",
"author": [ "Thomas H Cormen", "Charles E Leiserson", "Ronald L Riverst", "Clifford Stein" ] } ]
}
}
)
db.Subject.insert(
{
"_id":ObjectId(),
"subject":{
"subCode":"IACT201",
"subTitle":"Professional Practice and Ethics",
"credit":3,
"type":"Elective",
"assessments": [
{ "assessNum": 1,
"weight":35,
"assessType":"Assignment",
"description":"Assignment 1 - Ethical Dilemma Case Study" },
{ "assignNum": 2,
"weight":25,
"assessType":"Presentation",
"description":"Presentation of Case Study" },
{ "assessNum": 3,
"weight": 40,
"assessType":"Examination",
"description":"Closed-book Final Examination" }
]
}
}
)
db.Subject.insert(
{
"_id":ObjectId(),
"subject":{
"subCode":"CSCI321",
"subTitle":"Final Year Project",
"credit":6,
"type":"Core",
"assessments": [
{ "assessNum": 1,
"weight":30,
"assessType":"Presentation",
"description":"Prototype demonstration" },
{ "assignNum": 2,
"weight":70,
"assessType":"Implementation and Presentation",
"description":"Final product Presentation and assessment of product implementation by panel of project supervisors" }
]
}
}
)
【问题讨论】：
标签： arrays mongodb aggregation-framework