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To coalesce values means to merge them. To merge them into a single array, use $project in MongoDB.Let us create a collection with documents −> db.demo244.insertOne({"Value1":10, "Value2":20}); { "acknowledged" : true, "insertedId" : ObjectId("5e4582e31627c0c63e7dba63") } > db.demo244.insertOne({"Value1":20, "Value2":30}); { "acknowledged" : true, "insertedId" : ObjectId("5e4582f11627c0c63e7dba64") }Display all documents from a collection with the help of find() method −> db.demo244.find();This will produce the following output −{ "_id" : ObjectId("5e4582e31627c0c63e7dba63"), "Value1" : 10, "Value2" : 20 } { "_id" : ObjectId("5e4582f11627c0c63e7dba64"), "Value1" : 20, "Value2" : 30 }Following is the query to coalesce values from different properties into ... Read More
For this, simply use aggregate() in MongoDB. Let us create a collection with documents −> db.demo243.insertOne({"userId":1, dueDate:new ISODate("2019-01-10")}); { "acknowledged" : true, "insertedId" : ObjectId("5e4575f81627c0c63e7dba5f") } > db.demo243.insertOne({"userId":2, dueDate:new ISODate("2019-11-10")}); { "acknowledged" : true, "insertedId" : ObjectId("5e4576011627c0c63e7dba60") } > db.demo243.insertOne({"userId":2, dueDate:new ISODate("2020-01-31")}); { "acknowledged" : true, "insertedId" : ObjectId("5e4576151627c0c63e7dba61") } > db.demo243.insertOne({"userId":1, dueDate:new ISODate("2010-01-10")}); { "acknowledged" : true, "insertedId" : ObjectId("5e45761b1627c0c63e7dba62") }Display all documents from a collection with the help of find() method −> db.demo243.find();This will produce the following output −{ "_id" : ObjectId("5e4575f81627c0c63e7dba5f"), "userId" : 1, "dueDate" : ISODate("2019-01-10T00:00:00Z") } { ... Read More
The easiest way to sort an array in MongoDB, use $sort. Let us create a collection with documents −> db.demo242.insertOne( ... ... {"details2": ... [ ... {"ShipingDate":new ISODate("2019-10-11"), "Price":1400}, ... {"ShipingDate":new ISODate("2019-10-01"), "Price":1600 } ... ] ... } ... ...); { "acknowledged" : true, "insertedId" : ObjectId("5e4429229af932883c61ea44") }Display all documents from a collection with the help of find() method −> db.demo242.find();This will produce the following output −{ "_id" : ObjectId("5e4429229af932883c61ea44"), "details2" : [ { "ShipingDate" : ISODate("2019-10-11T00:00:00Z"), "Price" : 1400 ... Read More
To get the maximum marks records, use sort() in descending order along with limit 1. Let us create a collection with documents −> db.demo241.insertOne({"Marks":67}); { "acknowledged" : true, "insertedId" : ObjectId("5e441f729af932883c61ea40") } > db.demo241.insertOne({"Marks":89}); { "acknowledged" : true, "insertedId" : ObjectId("5e441f769af932883c61ea41") } > db.demo241.insertOne({"Marks":78}); { "acknowledged" : true, "insertedId" : ObjectId("5e441f789af932883c61ea42") }Display all documents from a collection with the help of find() method −> db.demo241.find();This will produce the following output −{ "_id" : ObjectId("5e441f729af932883c61ea40"), "Marks" : 67 } { "_id" : ObjectId("5e441f769af932883c61ea41"), "Marks" : 89 } { "_id" : ObjectId("5e441f789af932883c61ea42"), "Marks" : 78 }Following ... Read More
To limit the number of records, use $limit in MongoDB. Let us create a collection with documents −> db.demo240.insertOne({"StudentName":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e441d969af932883c61ea3c") } > db.demo240.insertOne({"StudentName":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e441d9a9af932883c61ea3d") } > db.demo240.insertOne({"StudentName":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e441d9d9af932883c61ea3e") } > db.demo240.insertOne({"StudentName":"Mike"}); { "acknowledged" : true, "insertedId" : ObjectId("5e441da19af932883c61ea3f") }Display all documents from a collection with the help of find() method −> db.demo240.find();This will produce the following output −{ "_id" : ObjectId("5e441d969af932883c61ea3c"), "StudentName" : "Chris" } { "_id" : ObjectId("5e441d9a9af932883c61ea3d"), "StudentName" : "Bob" } { ... Read More
To limit the number of records, use $limit in MongoDB. Let us create a collection with documents −> db.demo240.insertOne({"StudentName":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e441d969af932883c61ea3c") } > db.demo240.insertOne({"StudentName":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e441d9a9af932883c61ea3d") } > db.demo240.insertOne({"StudentName":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e441d9d9af932883c61ea3e") } > db.demo240.insertOne({"StudentName":"Mike"}); { "acknowledged" : true, "insertedId" : ObjectId("5e441da19af932883c61ea3f") }Display all documents from a collection with the help of find() method −> db.demo240.find();This will produce the following output −{ "_id" : ObjectId("5e441d969af932883c61ea3c"), "StudentName" : "Chris" } { "_id" : ObjectId("5e441d9a9af932883c61ea3d"), "StudentName" : "Bob" } { ... Read More
For such cases, use $elemMatch. This operator matches documents that contain an array field with at least one element that matches all the specified query criteria.Let us create a collection with documents −> db.demo239.insertOne( ... { ... "Name" : "Chris", ... "details" : [ ... { "DueDate" : new ISODate("2019-01-21"), "ProductPrice" : 1270 }, ... { "DueDate" : new ISODate("2020-02-12"), "ProductPrice" : 2000 } ... ] ... } ...); { "acknowledged" : true, "insertedId" : ObjectId("5e441c6bf4cebbeaebec5157") } > db.demo239.insertOne( ... { ... Read More
The $unwind in MongoDB deconstructs an array field from the input documents to output a document for each element.$group is used to group input documents by the specified _id expression and for each distinct grouping, outputs a document.$project is used to pass along the documents with the requested fields to the next stage in the pipeline.Let us create a collection with documents −> db.demo238.insertOne( ... { ... ... "EmailId" : "John@gmail.com", ... "details" : [ ... { ... "Name" : "Bob", ... ... Read More
Set the field you don’t want to include as 0. This would display rest of the values while using find(). Let us first create a collection with documents −> db.demo237.insertOne({ ... _id:101, ... Product: { ... description1: {id:1001 }, ... description2: {Name:"Product-1" }, ... description3: {Price:550 } ... } ...} ...); { "acknowledged" : true, "insertedId" : 101 }Display all documents from a collection with the help of find() method −> db.demo237.find().pretty();This will produce the following output −{ "_id" : 101, "Product" : { "description1" : ... Read More
To sort, use $sort in MongoDB. Let us create a collection with documents −> db.demo236.insertOne({"details":{"Name":"Chris", "Age":21}}); { "acknowledged" : true, "insertedId" : ObjectId("5e419015f4cebbeaebec514c") } > db.demo236.insertOne({"details":{"Name":"David", "Age":23}}); { "acknowledged" : true, "insertedId" : ObjectId("5e41901cf4cebbeaebec514d") } > db.demo236.insertOne({"details":{"Name":"Bob", "Age":24}}); { "acknowledged" : true, "insertedId" : ObjectId("5e419023f4cebbeaebec514e") }Display all documents from a collection with the help of find() method −> db.demo236.find();This will produce the following output −{ "_id" : ObjectId("5e419015f4cebbeaebec514c"), "details" : { "Name" : "Chris", "Age" : 21 } } { "_id" : ObjectId("5e41901cf4cebbeaebec514d"), "details" : { "Name" : "David", "Age" : 23 } } ... Read More