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Apply a condition inside subset in MongoDB Aggregation?
To apply a condition, use $setIsSubset. Let us first create a collection with documents −
> db.subsetDemo.insertOne({"StudentName":"Chris","StudentFavouriteSubject":["Java","Python"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e063e49150ee0e76c06a052")
}
> db.subsetDemo.insertOne({"StudentName":"Chris","StudentFavouriteSubject":["Java","Python","MySQL"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e063e4f150ee0e76c06a053")
}Following is the query to display all documents from a collection with the help of find() method −
> db.subsetDemo.find().pretty();
This will produce the following output −
{
"_id" : ObjectId("5e063e49150ee0e76c06a052"),
"StudentName" : "Chris",
"StudentFavouriteSubject" : [
"Java",
"Python"
]
}
{
"_id" : ObjectId("5e063e4f150ee0e76c06a053"),
"StudentName" : "Chris",
"StudentFavouriteSubject" : [
"Java",
"Python",
"MySQL"
]
}Here is the query to apply condition inside subset in MongoDB aggregation −
> db.subsetDemo.aggregate([
... {
... $project: {
... _id: 0,
... StudentName: 1,
... isMySQL: {
... $setIsSubset: [["MySQL"], "$StudentFavouriteSubject"]
... }
... }
... }
... ]);This will produce the following output −
{ "StudentName" : "Chris", "isMySQL" : false }
{ "StudentName" : "Chris", "isMySQL" : true }
Updated on: 27-Mar-2020
246 Views
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