To get distinct values, use distinct() in MongoDB. It finds the distinct values for a specified field across a single collection or view and returns the results in an array.Let us create a collection with documents −> db.demo287.insertOne({"details":{"AllVowels":["a", "u", "u", "o", "e", "a", "o", "i"]}}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e4c014cf49383b52759cbbd") }Display all documents from a collection with the help of find() method −> db.demo287.find().pretty();This will produce the following output −{    "_id" : ObjectId("5e4c014cf49383b52759cbbd"),    "details" : {       "AllVowels" : [ "a", "u", "u", "o", "e", "a", "o", "i" ]    } }Following ... Read More

To get the min and max values, use $min and $max. Let us create a collection with documents −> db.demo286.insertOne({"details":[{Value1:70, Value2:50}, {Value1:30, Value2:36}]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e4ac743f49383b52759cbbc") }Display all documents from a collection with the help of find() method −> db.demo286.find().pretty();This will produce the following output −{    "_id" : ObjectId("5e4ac743f49383b52759cbbc"),    "details" : [       {          "Value1" : 70,          "Value2" : 50       },       {          "Value1" : 30,          "Value2" : 36 ... Read More

The command you can use is db.runCommand(). Let us first switch to admin −> use admin switched to db adminNow, run the command −> db.runCommand({listDatabases : 1})This will produce the following output −{    "databases" : [       {          "name" : "admin",          "sizeOnDisk" : 2375680,          "empty" : false       },       {          "name" : "app",          "sizeOnDisk" : 32768,          "empty" : false       },       {   ... Read More

For this, use aggregate() in MongoDB. Let us create a collection with documents −> db.demo285.insertOne( ...   {... details : [ ...      { ...         Name : "Chris" ...      }, ...      { ...         Name2: "Bob" ...      }, ...      { ...         Name: "Mike" ...      } ...   ] ...   } ...) {    "acknowledged" : true,    "insertedId" : ObjectId("5e4abffef49383b52759cbb9") }Display all documents from a collection with the help of find() method −> db.demo285.find();This will produce the ... Read More

To export MongoDB has a command mongoexport. Following is the syntax −mongoexport -d yourDatabaseName -c yourCollectionName -f yourFieldName --type=csv -o yourFileLocation/FileName;Let us create a collection with documents −> db.demo284.insertOne({"FirstName":"Chris"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e4abc9e9127fafea82a2cfc") } > db.demo284.insertOne({"FirstName":"Robert"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e4abca39127fafea82a2cfd") } > db.demo284.insertOne({"FirstName":"Bob"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e4abca79127fafea82a2cfe") }Display all documents from a collection with the help of find() method −> db.demo284.find();This will produce the following output −{ "_id" : ObjectId("5e4abc9e9127fafea82a2cfc"), "FirstName" : "Chris" } { "_id" : ObjectId("5e4abca39127fafea82a2cfd"), "FirstName" : "Robert" } { "_id" : ... Read More

To update array with another field, use $push. Let us create a collection with documents −> db.demo283.insertOne({"Name":"Chris", "Status":["Active", "Inactive"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e4ab97ddd099650a5401a75") }Display all documents from a collection with the help of find() method −> db.demo283.find();This will produce the following output −{ "_id" : ObjectId("5e4ab97ddd099650a5401a75"), "Name" : "Chris", "Status" : [ "Active", "Inactive" ] }Following is the query to update array with another field −> db.demo283.update({}, {$push: {Status:{$each:['Regular', 'NotRegular'], '$slice': -4}}}); WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })Display all documents from a collection with the help of find() method −> ... Read More

To retrieve document from collection by _id, use find() with $in. Let us create a collection with documents −> db.demo281.insertOne({"Name":"Chris", "Age":21}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e4aac28dd099650a5401a66") } > db.demo281.insertOne({"Name":"Bob", "Age":23}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e4aac46dd099650a5401a67") } > db.demo281.insertOne({"Name":"David", "Age":28}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e4aac4fdd099650a5401a68") }Display all documents from a collection with the help of find() method −> db.demo281.find();This will produce the following output −{ "_id" : ObjectId("5e4aac28dd099650a5401a66"), "Name" : "Chris", "Age" : 21 } { "_id" : ObjectId("5e4aac46dd099650a5401a67"), "Name" : "Bob", "Age" : 23 } { "_id" : ... Read More

To delete element from an array, use $pull. Let us create a collection with documents −> db.demo279.insertOne({id:[101, 103, 105, 110]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e490af7dd099650a5401a58") } > db.demo279.insertOne({id:[107, 111, 110]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e490b06dd099650a5401a59") }Display all documents from a collection with the help of find() method −> db.demo279.find();This will produce the following output −{ "_id" : ObjectId("5e490af7dd099650a5401a58"), "id" : [ 101, 103, 105, 110 ] } { "_id" : ObjectId("5e490b06dd099650a5401a59"), "id" : [ 107, 111, 110 ] }Following is the query to delete element from an array &minus';> db.demo279.update({}, {$pull:{id:110}}, {multi:true}); ... Read More

Create an index and then use explain(). Let us create a collection with documents −> db.demo278.ensureIndex({"Subjects":1}); {    "createdCollectionAutomatically" : true,    "numIndexesBefore" : 1,    "numIndexesAfter" : 2,    "ok" : 1 } > db.demo278.insertOne({"Subjects":["MySQL", "MongoDB", "Java"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e49096edd099650a5401a55") } > db.demo278.insertOne({"Subjects":["C", "C++"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e490978dd099650a5401a56") } > db.demo278.insertOne({"Subjects":["Spring", "Hibernate"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e490984dd099650a5401a57") }Display all documents from a collection with the help of find() method −> db.demo278.find();This will produce the following output −{ "_id" : ObjectId("5e49096edd099650a5401a55"), "Subjects" : [ "MySQL", ... Read More

Let us first create a collection with documents −> db.demo277.insertOne({"details":[{"FirstName":"John"}]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e48fb21dd099650a5401a52") } > db.demo277.insertOne({"details":[{"FirstName":"David"}]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e48fb27dd099650a5401a53") } > db.demo277.insertOne({"details":[{"FirstName":"Chris"}]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e48fb2bdd099650a5401a54") }Display all documents from a collection with the help of find() method −> db.demo277.find();This will produce the following output −{ "_id" : ObjectId("5e48fb21dd099650a5401a52"), "details" : [ { "FirstName" : "John" } ] } { "_id" : ObjectId("5e48fb27dd099650a5401a53"), "details" : [ { "FirstName" : "David" } ] } { "_id" : ObjectId("5e48fb2bdd099650a5401a54"), "details" : [ { "FirstName" : ... Read More