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How can I find documents in MongoDB based on the number of matched objects within an array?
Let us see an example and create a collection with documents −
> db.demo694.insertOne(
... {
... "details" :
... [
... {
... "Name" : "Chris",
... Age:21
... },
... {
... "Name" : "David",
... Age:22
... }
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5ea59279ece4e5779399c07f")
}
> db.demo694.insertOne(
... {
... "details" :
... [
... {
... "Name" : "Bob",
... Age:21
... },
... {
... "Name" : "Mike",
... Age:23
... }
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5ea5927aece4e5779399c080")
}
> db.demo694.insertOne(
... {
... "details" :
... [
... {
... "Name" : "Chris",
... Age:21
... },
... {
... "Name" : "Carol",
... Age:22
... }
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5ea5927aece4e5779399c081")
}Display all documents from a collection with the help of find() method −
> db.demo694.find();
This will produce the following output −
{ "_id" : ObjectId("5ea59279ece4e5779399c07f"), "details" : [ { "Name" : "Chris", "Age" : 21 }, { "Name" : "David", "Age" : 22 } ] }
{ "_id" : ObjectId("5ea5927aece4e5779399c080"), "details" : [ { "Name" : "Bob", "Age" : 21 }, { "Name" : "Mike", "Age" : 23 } ] }
{ "_id" : ObjectId("5ea5927aece4e5779399c081"), "details" : [ { "Name" : "Chris", "Age" : 21 }, { "Name" : "Carol", "Age" : 22 } ] }Following is the query to find documents in MongoDB based on the number of matched objects within an array −
> nameChrisAge21= function () {
... var inc = 0;
... this.details.forEach(function (d) {
... if (d.Name == "Chris" && d.Age == 21) {
... inc= inc + 1;
... }
... });
... if (inc >= 1) {
... return true;
... }
... }
function () {
var inc = 0;
this.details.forEach(function (d) {
if (d.Name == "Chris" && d.Age == 21) {
inc= inc + 1;
}
});
if (inc >= 1) {
return true;
}
}
> db.demo694.find({$where:nameChrisAge21});This will produce the following output −
{ "_id" : ObjectId("5ea59279ece4e5779399c07f"), "details" : [ { "Name" : "Chris", "Age" : 21 }, { "Name" : "David", "Age" : 22 } ] }
{ "_id" : ObjectId("5ea5927aece4e5779399c081"), "details" : [ { "Name" : "Chris", "Age" : 21 }, { "Name" : "Carol", "Age" : 22 } ] }
Updated on: 14-May-2020
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