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Selecting only a single field from MongoDB?
You can use $and operator. Let us first create a collection with documents −
>db.selectingASingleFieldDemo.insertOne({"StudentFirstName":"John","StudentAge":23,"StudentCountryName":"US"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd547142cba06f46efe9f02")
}
>db.selectingASingleFieldDemo.insertOne({"StudentFirstName":"Carol","StudentAge":21,"StudentCountryName":"UK"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd5471f2cba06f46efe9f03")
}
>db.selectingASingleFieldDemo.insertOne({"StudentFirstName":"David","StudentAge":24,"StudentCountryName":"AUS"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd5472c2cba06f46efe9f04")
}
>db.selectingASingleFieldDemo.insertOne({"StudentFirstName":"Robert","StudentAge":26,"StudentCountryName":"AUS"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd548382cba06f46efe9f05")
}Following is the query to display all documents from a collection with the help of find() method −
> db.selectingASingleFieldDemo.find().pretty();
This will produce the following output −
{
"_id" : ObjectId("5cd547142cba06f46efe9f02"),
"StudentFirstName" : "John",
"StudentAge" : 23,
"StudentCountryName" : "US"
}
{
"_id" : ObjectId("5cd5471f2cba06f46efe9f03"),
"StudentFirstName" : "Carol",
"StudentAge" : 21,
"StudentCountryName" : "UK"
}
{
"_id" : ObjectId("5cd5472c2cba06f46efe9f04"),
"StudentFirstName" : "David",
"StudentAge" : 24,
"StudentCountryName" : "AUS"
}
{
"_id" : ObjectId("5cd548382cba06f46efe9f05"),
"StudentFirstName" : "Robert",
"StudentAge" : 26,
"StudentCountryName" : "AUS"
}Following is the query to select only a single field from MongoDB −
> db.selectingASingleFieldDemo.find(
... { $and:[{StudentAge: { $gt:21 } },
... {"StudentCountryName" : "AUS"}] },
... {StudentFirstName: 1, _id: 0});This will produce the following output −
{ "StudentFirstName" : "David" }
{ "StudentFirstName" : "Robert" }
Updated on: 30-Jul-2019
342 Views
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