MongoDB查询以获取数组值
使用find()连同$elemMatch获取数组值。首先让我们创建一个包含文档的集合-
> db.fetchingArrayValuesDemo.insertOne(
... {
... "StudentName": "David",
... "StudentDetails": [
... {
... "FatherName": "Bob",
... "CountryName": "US",
...
... "Favourite": [
... {
... "Teacher": "DAVID",
... "Subject": [
... "MySQL",
... "MongoDB",
... "Java"
... ],
... "Marks": [
... 50,
... 60,
... 65
... ]
... }
... ]
...
... }
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e06fc3425ddae1f53b621fa")
}
> db.fetchingArrayValuesDemo.insertOne(
... {
... "StudentName": "Robert",
... "StudentDetails": [
... {
... "FatherName": "Sam",
... "CountryName": "AUS",
...
... "Favourite": [
... {
... "Teacher": "MIKE",
... "Subject": [
... "Python",
... "C",
... "C++"
... ],
... "Marks": [
... 76,
... 89,
... 91
... ]
... }
... ]
...
... }
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e06fc6825ddae1f53b621fb")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.fetchingArrayValuesDemo.find();
这将产生以下输出-
{ "_id" : ObjectId("5e06fc3425ddae1f53b621fa"), "StudentName" : "David", "StudentDetails" : [ { "FatherName" : "Bob", "CountryName" : "US", "Favourite" : [ { "Teacher" : "DAVID", "Subject" : [ "MySQL", "MongoDB", "Java" ], "Marks" : [ 50, 60, 65 ] } ] } ] }
{ "_id" : ObjectId("5e06fc6825ddae1f53b621fb"), "StudentName" : "Robert", "StudentDetails" : [ { "FatherName" : "Sam", "CountryName" : "AUS", "Favourite" : [ { "Teacher" : "MIKE", "Subject" : [ "Python", "C", "C++" ], "Marks" : [ 76, 89, 91 ] } ] } ] }这是获取数组值的查询-
> db.fetchingArrayValuesDemo.find({
... StudentDetails:{
... $elemMatch: {
... Favourite: {
... $elemMatch: {
... Teacher: "DAVID"
... }
... }
... }
... }
... });这将产生以下输出-
{ "_id" : ObjectId("5e06fc3425ddae1f53b621fa"), "StudentName" : "David", "StudentDetails" : [ { "FatherName" : "Bob", "CountryName" : "US", "Favourite" : [ { "Teacher" : "DAVID", "Subject" : [ "MySQL", "MongoDB", "Java" ], "Marks" : [ 50, 60, 65 ] } ] } ] }