在MongoDB的子文档中查找特定项目？
要在sudocument中获取特定项目，请使用dot（。）表示法。让我们创建一个包含文档的集合-
> db.demo81.insertOne({"StudentDetails":[{"StudentName":"Carol","StudentSubject":"Java"},{ "StudentName" : "David", "StudentSubject" : "MongoDB" }]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e2bf6ec71bf0181ecc4229d")
}
> db.demo81.insertOne({"StudentDetails":[{"StudentName":"Mike","StudentSubject":"Python"},{ "StudentName" : "David", "StudentSubject" : "C" }]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e2bf70471bf0181ecc4229e")
}
> db.demo81.insertOne({"StudentDetails":[{"StudentName":"Jace","StudentSubject":"C++"},{ "StudentName" : "John", "StudentSubject" : "MySQL" }]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e2bf72071bf0181ecc4229f")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo81.find();
这将产生以下输出-
{
"_id" : ObjectId("5e2bf6ec71bf0181ecc4229d"), "StudentDetails" : [
{ "StudentName" : "Carol", "StudentSubject" : "Java" },
{"StudentName" : "David", "StudentSubject" : "MongoDB" }
]
}
{
"_id" : ObjectId("5e2bf70471bf0181ecc4229e"), "StudentDetails" : [
{ "StudentName" : "Mike", "StudentSubject" : "Python" },
{ "StudentName" : "David", "StudentSubject" : "C" }
]
}
{
"_id" : ObjectId("5e2bf72071bf0181ecc4229f"), "StudentDetails" : [
{ "StudentName" : "Jace", "StudentSubject" : "C++" },
{ "StudentName" : "John", "StudentSubject" : "MySQL" }
]
}以下是使用MongoDB在子文档中查找项目的查询-
> db.demo81.find({"StudentDetails.StudentSubject":"MongoDB"});这将产生以下输出-
{ "_id" : ObjectId("5e2bf6ec71bf0181ecc4229d"), "StudentDetails" : [ { "StudentName" : "Carol", "StudentSubject" : "Java" }, { "StudentName" : "David", "StudentSubject" : "MongoDB" } ] }