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Database Articles
Page 476 of 546
Return True if a document exists in MongoDB?
Let us first create a collection. Following is the query to create a collection with documents> db.documentExistsOrNotDemo.insertOne({"UserId":101, "UserName":"John"}); { "acknowledged" : true, "insertedId" : ObjectId("5c9932bd330fd0aa0d2fe4cf") } > db.documentExistsOrNotDemo.insertOne({"UserId":102, "UserName":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5c9932c6330fd0aa0d2fe4d0") } > db.documentExistsOrNotDemo.insertOne({"UserId":102, "UserName":"Robert"}); { "acknowledged" : true, "insertedId" : ObjectId("5c9932ce330fd0aa0d2fe4d1") }Following is the query to display all the documents from a collection with the help of find() method> db.documentExistsOrNotDemo.find().pretty();This will produce the following output{ "_id" : ObjectId("5c9932bd330fd0aa0d2fe4cf"), "UserId" : 101, "UserName" : "John" } { "_id" : ObjectId("5c9932c6330fd0aa0d2fe4d0"), "UserId" : 102, ...
Read MoreCan I get the first item in a Cursor object in MongoDB?
Yes, you can get the first item in a cursor object using findOne() method. Following is the syntaxdb.yourCollectionName.findOne();However, the following syntax is used if you want a single document in a cursor objectdb.yourCollectionName.findOne({yourCondition});We will first create a collection. Following is the query to create a collection with documents> db.getFirstItemDemo.insertOne({"CustomerName":"Chris", "CustomerAge":28}); { "acknowledged" : true, "insertedId" : ObjectId("5c989059330fd0aa0d2fe4c1") } > db.getFirstItemDemo.insertOne({"CustomerName":"Larry", "CustomerAge":26}); { "acknowledged" : true, "insertedId" : ObjectId("5c989063330fd0aa0d2fe4c2") } > db.getFirstItemDemo.insertOne({"CustomerName":"Robert", "CustomerAge":29}); { "acknowledged" : true, "insertedId" : ObjectId("5c98906d330fd0aa0d2fe4c3") } > db.getFirstItemDemo.insertOne({"CustomerName":"David", "CustomerAge":39}); { "acknowledged" : true, "insertedId" : ObjectId("5c989081330fd0aa0d2fe4c4") }Following is ...
Read MoreDrop all indexes from all the collections in a MongoDB database using the command line?
Following is the syntax to drop all indexes from all collections in a MongoDB database using command linedb.getCollectionNames().forEach(function(yourVariableName) { db.runCommand({dropIndexes: yourVariableName, index: "*"}); });The above syntax will drop all indexes except _id.Let us check the current database. Following is the query> dbThis will produce the following outputTestFollowing is the query to let us show some indexes from a collection before dropping indexes> db.indexingDemo.getIndexes();This will produce the following output[ { "v" : 2, "key" : { "_id" : 1 }, "name" : "_id_", ...
Read MoreHow to get all the collections from all the MongoDB databases?
To get all the collections from all the databases, let us first get all the databases using the following query> switchDatabaseAdmin = db.getSiblingDB("admin"); admin > allDatabaseName = switchDatabaseAdmin.runCommand({ "listDatabases": 1 }).databases;This will produce the following output[ { "name" : "admin", "sizeOnDisk" : 495616, "empty" : false }, { "name" : "config", "sizeOnDisk" : 98304, "empty" : false }, { "name" : "local", "sizeOnDisk" : 73728, "empty" : false ...
Read MoreSearch for a text in MongoDBs Double Nested Array?
Search for a text in MongoDBs Double Nested Array with the help of dot(.) notation. Let us first create a collection. Following is the query to create a collection with documents> db.doubleNestedArrayDemo.insertOne( ... { ... "StudentId" : "1000", ... "StudentName" : "Larry", ... "StudentDetails" : [ ... { ... "ProjectName" : "Online Banking", ... "ProjectDetails" : [ ... { ... ...
Read MoreGet all the MongoDB documents but not the ones with two given criteria’s?
To get all the MongoDB documents with some given criteria’s, following any of the below given casesCase 1 Following is the query to get all the documents without a single criterion using $ne operatordb.yourCollectionName.find({yourFieldName:{$ne:"yourValue"}}).pretty();Case 2 Following is the query to get all the documents without two given criterions using $nin operatordb.yourCollectionName.find({yourFieldName:{$nin:["yourValue1", "yourValue2"]}}).pretty();Let us first create a collection. Following is the query to create a collection with documents>db.findAllExceptFromOneOrtwoDemo.insertOne({"StudentName":"Larry", "StudentSubjectName":"Java"}); { "acknowledged" : true, "insertedId" : ObjectId("5c993d82330fd0aa0d2fe4d2") } >db.findAllExceptFromOneOrtwoDemo.insertOne({"StudentName":"Chris", "StudentSubjectName":"C++"}); { "acknowledged" : true, "insertedId" : ObjectId("5c993d8f330fd0aa0d2fe4d3") } >db.findAllExceptFromOneOrtwoDemo.insertOne({"StudentName":"Robert", "StudentSubjectName":"C"}); { "acknowledged" : true, "insertedId" : ObjectId("5c993d99330fd0aa0d2fe4d4") } ...
Read MoreSearch multiple fields for multiple values in MongoDB?
To search multiple fields for multiple values in MongoDB, you can use $text and $search operator. Let us first create a collection with documents>db.searchMultipleFieldsDemo.insertOne({"_id":100, "FirstSubject":"Java", "SecondSubject":"MongoDB"}); { "acknowledged" : true, "insertedId" : 100 } >db.searchMultipleFieldsDemo.insertOne({"_id":101, "FirstSubject":"MongoDB", "SecondSubject":"MySQL"}); { "acknowledged" : true, "insertedId" : 101 } >db.searchMultipleFieldsDemo.insertOne({"_id":102, "FirstSubject":"MySQL", "SecondSubject":"Java"}); { "acknowledged" : true, "insertedId" : 102 }Following is the query to display all documents from a collection with the help of find() method> db.searchMultipleFieldsDemo.find().pretty();This will produce the following output{ "_id" : 100, "FirstSubject" : "Java", "SecondSubject" : "MongoDB" } { "_id" : 101, "FirstSubject" : "MongoDB", "SecondSubject" : "MySQL" } { ...
Read MoreHow to create an index with MongoDB?
To create an index in MongoDB, use the ensureIndex() method. Let us first create a collection using following query> db.createCollection(&qu/ot;creatingUniqueIndexDemo"); { "ok" : 1 }Following is the query to create an index on the above collection:> db.creatingUniqueIndexDemo.ensureIndex({"UserCountryName":1}, {unique:true}); { "createdCollectionAutomatically" : false, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 }Following is the query to insert some documents in the above collection>db.creatingUniqueIndexDemo.insertOne({"UserName":"John", "UserAge":21, "UserCountryName":"US"}); { "acknowledged" : true, "insertedId" : ObjectId("5c9947bd330fd0aa0d2fe4d8") } >db.creatingUniqueIndexDemo.insertOne({"UserName":"Mike", "UserAge":23, "UserCountryName":"UK"}); { "acknowledged" : true, "insertedId" : ObjectId("5c9947c9330fd0aa0d2fe4d9") } >db.creatingUniqueIndexDemo.insertOne({"UserName":"Robert", "UserAge":26, "UserCountryName":"US"}); 2019-03-26T02:57:52.670+0530 E QUERY [js] WriteError: ...
Read MoreHow can I to know if my database MongoDB is 64 bits?
You can use buidInfo along with runCommand to check MongoDB for 32 bits or 64 bits. First switch your database to admin. Following is the syntaxuse adminAfter that use the following syntax to know if my server runs MongoDB 64 bits or notdb.runCommand(buildInfo)Now execute the above syntax> use admin switched to db admin > db.runCommand("buildInfo");Following is the output displaying MongoDB is 64 bits{ "version" : "4.0.5", "gitVersion" : "3739429dd92b92d1b0ab120911a23d50bf03c412", "targetMinOS" : "Windows 7/Windows Server 2008 R2", "modules" : [ ], "allocator" : "tcmalloc", "javascriptEngine" : "mozjs", "sysInfo" : "deprecated", "versionArray" : [ ...
Read MoreFind all the non-distinct values of a field in MongoDB?
Use aggregate() method to get all the non-distinct values of a field. Let us first create a collection with documents> db.findAllNonDistinctDemo.insertOne({"UserName":"John", "UserAge":28}); { "acknowledged" : true, "insertedId" : ObjectId("5c995078863d6ffd454bb647") } > db.findAllNonDistinctDemo.insertOne({"UserName":"Larry", "UserAge":21}); { "acknowledged" : true, "insertedId" : ObjectId("5c995081863d6ffd454bb648") } > db.findAllNonDistinctDemo.insertOne({"UserName":"Larry", "UserAge":23}); { "acknowledged" : true, "insertedId" : ObjectId("5c995089863d6ffd454bb649") } > db.findAllNonDistinctDemo.insertOne({"UserName":"David", "UserAge":22}); { "acknowledged" : true, "insertedId" : ObjectId("5c995093863d6ffd454bb64a") } > db.findAllNonDistinctDemo.insertOne({"UserName":"John", "UserAge":26}); { "acknowledged" : true, "insertedId" : ObjectId("5c99509d863d6ffd454bb64b") } > db.findAllNonDistinctDemo.insertOne({"UserName":"Robert", "UserAge":24}); { "acknowledged" : true, "insertedId" : ObjectId("5c9950a7863d6ffd454bb64c") } > db.findAllNonDistinctDemo.insertOne({"UserName":"Robert", "UserAge":25}); ...
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