To match a specific field value, use a $match in MongoDB aggregation. Let us create a collection with documents −> db.demo555.insertOne({"CountryName":"US"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8f21bf54b4472ed3e8e85f") } > db.demo555.insertOne({"CountryName":"UK"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8f21c254b4472ed3e8e860") } > db.demo555.insertOne({"CountryName":"US"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8f21c354b4472ed3e8e861") } > db.demo555.insertOne({"CountryName":"AUS"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8f21c554b4472ed3e8e862") } > db.demo555.insertOne({"CountryName":"US"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8f21c754b4472ed3e8e863") }Display all documents from a collection with the help of find() method −> db.demo555.find();This will produce the following output: −{ "_id" : ObjectId("5e8f21bf54b4472ed3e8e85f"), "CountryName" : "US" } { "_id" : ObjectId("5e8f21c254b4472ed3e8e860"), "CountryName" ... Read More

For “like” implementation in MongoDB, use / / and set that specific letter in between. For example −/J/Let us create a collection with documents −> db.demo554.insertOne({"UserName":"John", "UserMailId":"John@gmail.com"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8f1cfed1d72c4545cb8679") } > db.demo554.insertOne({"UserName":"Chris", "UserMailId":"Chris@gmail.com"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8f1d0cd1d72c4545cb867a") } > db.demo554.insertOne({"UserName":"Jace", "UserMailId":"Jace@gmail.com"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8f1d1cd1d72c4545cb867b") }Display all documents from a collection with the help of find() method −> db.demo554.find();This will produce the following output −{ "_id" : ObjectId("5e8f1cfed1d72c4545cb8679"), "UserName" : "John", "UserMailId" : "John@gmail.com" } { "_id" : ObjectId("5e8f1d0cd1d72c4545cb867a"), "UserName" : "Chris", "UserMailId" : "Chris@gmail.com" } { "_id" : ... Read More

For this, use findOneAndUpdate() in MongoDB. The findOneAndUpdate() method updates a single document based on the filter and sort criteria.Let us create a collection with documents −> db.demo553.insertOne( ... { ...    id:101, ...    "Name":"John", ...    midExamDetails: ...    [ ...       {"SubjectName":"MySQL", "Marks":70}, ...       {"SubjectName":"MongoDB", "Marks":35} ...    ] ... } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e8e3da19e5f92834d7f05ed") }Display all documents from a collection with the help of find() method −> db.demo553.find();This will produce the following output −{ "_id" : ObjectId("5e8e3da19e5f92834d7f05ed"), "id" : 101, "Name" : "John", "midExamDetails" ... Read More

Use aggregate() in MongoDB to select documents with values above the average. To find the average, use $avg in MongoDB.Let us create a collection with documents −> db.demo552.insertOne({values:10});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e3b1c9e5f92834d7f05ea") } > db.demo552.insertOne({values:50});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e3b1f9e5f92834d7f05eb") } > db.demo552.insertOne({values:40});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e3b289e5f92834d7f05ec") }Display all documents from a collection with the help of find() method −> db.demo552.find();This will produce the following output −{ "_id" : ObjectId("5e8e3b1c9e5f92834d7f05ea"), "values" : 10 } { "_id" : ObjectId("5e8e3b1f9e5f92834d7f05eb"), "values" : 50 } { "_id" : ObjectId("5e8e3b289e5f92834d7f05ec"), "values" : 40 }Following is the ... Read More

For this, simply use $or once. Let us create a collection with documents −> db.demo551.insertOne({"Name":"John"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e36d39e5f92834d7f05e5") } > db.demo551.insertOne({"Name":"Chris Brown"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e36d89e5f92834d7f05e6") } > db.demo551.insertOne({"Name":"John Doe"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e36de9e5f92834d7f05e7") } > db.demo551.insertOne({"Name":"John Smith"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e36e59e5f92834d7f05e8") } > db.demo551.insertOne({"Name":"Carol"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e36ec9e5f92834d7f05e9") }Display all documents from a collection with the help of find() method −> db.demo551.find();This will produce the following output −{ "_id" : ObjectId("5e8e36d39e5f92834d7f05e5"), "Name" : "John" } { "_id" : ObjectId("5e8e36d89e5f92834d7f05e6"), "Name" : "Chris Brown" ... Read More

For this, use initializeOrderedBulkOp(). It initializes and returns a new Bulk() operations builder for a collection. The builder constructs an ordered list of write operations that MongoDB executes in bulk.Let us create a collection with documents −>db.demo550.insertOne({"Name":"Chris", "details":[{"Marks":49, Result:"fail"}, {"Marks":58, Result:"fail"}]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e8e35bd9e5f92834d7f05e4") }Display all documents from a collection with the help of find() method −> db.demo550.find();This will produce the following output −{ "_id" : ObjectId("5e8e35bd9e5f92834d7f05e4"), "Name" : "Chris", "details" : [ { "Marks" : 49, "Result" : "fail" }, { "Marks" : 58, "Result" : "fail" } ] }Following is the query ... Read More

To find a specific amount of records, use LIMIT() in MongoDB. The method accepts one number type argument, which is the number of documents that you want to be displayed.Let us create a collection with documents −> db.demo549.insertOne({"Name":"Chris"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e32889e5f92834d7f05df") } > db.demo549.insertOne({"Name":"David"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e328c9e5f92834d7f05e0") } > db.demo549.insertOne({"Name":"Bob"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e328f9e5f92834d7f05e1") } > db.demo549.insertOne({"Name":"John"});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e32929e5f92834d7f05e2") }Display all documents from a collection with the help of find() method −> db.demo549.find();This will produce the following output −{ "_id" : ObjectId("5e8e32889e5f92834d7f05df"), "Name" : ... Read More

The mongo shell provides various methods like ISODate() to return the date, either as a string or as a Date object. ISODate() constructor returns a Date object using the ISODate() wrapper.Let us create a collection with documents −> db.demo548.insertOne({"dueDate":new ISODate("2020-04-09 12:12:40")});{    "acknowledged" : true,    "insertedId" : ObjectId("5e8e30499e5f92834d7f05de") }Display all documents from a collection with the help of find() method −> db.demo548.find();This will produce the following output −{ "_id" : ObjectId("5e8e30499e5f92834d7f05de"), "dueDate" : ISODate("2020-04- 09T12:12:40Z") }Following is the query to display, month, day, week, year, etc. from ISODate −> db.demo548.aggregate( [ { $project: { Year: { $year: "$dueDate" }, ... Read More

For update, simply use update(). Use the $push operator to append a specified value and the dot notation to reach the sub collection and update inside update().Let us create a collection with documents −> db.demo547.insertOne( ... { ...    Name : "Chris", ...    Test : ...    { ...       "FirstTest" : ...       { ...          Scores: [56, 29, 76] ...       }, ...       "SecondTest" : ...       { ...          Scores: [98, 91, 78] ...       } ... ... Read More

The $redact restricts the contents of the documents based on information stored in the documents themselves. You can use $cond along with $redact in aggregate. Let us create a collection with documents −> db.demo546.insertOne({"Value1":10, "Value2":20});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e263f9e5f92834d7f05d7") } > db.demo546.insertOne({"Value1":40, "Value2":30, Value3:50});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e26549e5f92834d7f05d8") } > db.demo546.insertOne({"Value1":100, "Value2":200, Value3:null});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e26619e5f92834d7f05d9") } > db.demo546.insertOne({"Value1":400, "Value2":1000, Value3:null});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e26e09e5f92834d7f05da") } > db.demo546.insertOne({"Value1":400, "Value2":200, Value3:null});{    "acknowledged" : true, "insertedId" : ObjectId("5e8e26f59e5f92834d7f05db") } > db.demo546.insertOne({"Value1":400, "Value2":1000, Value3:60});{    "acknowledged" : true, "insertedId" ... Read More