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Database Articles
Page 188 of 546
How to get a rating average in MongoDB based on duplicate ids?
For average in MongoDB, use the $avg. Let us create a collection with documents. Here, we have duplicate ids with rating for each −> db.demo606.insertOne({id:1, rating:5});{ "acknowledged" : true, "insertedId" : ObjectId("5e972dfbf57d0dc0b182d623") } > db.demo606.insertOne({id:1, rating:4});{ "acknowledged" : true, "insertedId" : ObjectId("5e972dfef57d0dc0b182d624") } > db.demo606.insertOne({id:2, rating:3});{ "acknowledged" : true, "insertedId" : ObjectId("5e972e09f57d0dc0b182d625") } > db.demo606.insertOne({id:1, rating:null});{ "acknowledged" : true, "insertedId" : ObjectId("5e972e0ef57d0dc0b182d626") } > db.demo606.insertOne({id:2, rating:null});{ "acknowledged" : true, "insertedId" : ObjectId("5e972e15f57d0dc0b182d627") } > db.demo606.insertOne({id:2, rating:3});{ "acknowledged" : true, "insertedId" : ObjectId("5e972e1bf57d0dc0b182d628") }Display all documents from a collection with the help of find() method ...
Read MoreUpdate quantity in MongoDB based on two conditions?
For this, use UPDATE() method and within that set the two conditions. Let us create a collection with documents −> db.demo605.insertOne( ... { ... _id:1, ... "Information" : [ ... { ... "id" : "Product-1", ... "Quantity" : 50, ... }, ... { ... "id" : "Product-2", ... "Quantity" : 100, ... }, ...
Read MoreHow to remove duplicates from MongoDB Collection?
For this, set “unique:true” i.e. the unique constraint and avoid inserting duplicates as in the below syntax −db.yourCollectionName.ensureIndex({yourFieldName: 1}, {unique: true, dropDups: true})To understand the above syntax, let us create a collection with documents. Here, duplicate insertion won’t be allowed −> db.demo604.ensureIndex({FirstName: 1}, {unique: true, dropDups: true});{ "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.demo604.insertOne({FirstName:"Chris"});{ "acknowledged" : true, "insertedId" : ObjectId("5e960887ed011c280a0905d8") } > db.demo604.insertOne({FirstName:"Bob"});{ "acknowledged" : true, "insertedId" : ObjectId("5e96088aed011c280a0905d9") } > db.demo604.insertOne({FirstName:"David"});{ "acknowledged" : true, "insertedId" : ObjectId("5e96088ded011c280a0905da") } > db.demo604.insertOne({FirstName:"Chris"}); 2020-04-15T00:31:35.978+0530 ...
Read MoreDifference between NumberLong(x) and NumberLong(“x”) in MongoDB?
The NumberLong(x) goes beyond its limit value and round off the value whereas NumberLong(“x”) does not.Now, we will consider a number and would use it for both NumberLong(x) and NumberLong(“x”) to see the difference.Let us create a collection with documents −> db.demo603.insert({"longValue" : NumberLong(988998985857575789)}); WriteResult({ "nInserted" : 1 }) > db.demo603.insert({"longValueInString" : NumberLong("988998985857575789")});Display all documents from a collection with the help of find() method −> db.demo603.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e9605e5ed011c280a0905d1"), "longValue" : NumberLong("988998985857575808") } { "_id" : ObjectId("5e9605faed011c280a0905d2"), "longValueInString" : NumberLong("988998985857575789") }
Read MoreMongoDB aggregation of elements with similar ids in different documents?
For such grouping of documents, use $group in MongoDB aggregate(). Let us create a collection with documents −> db.demo602.insertOne({id:1, Name:"Chris"});{ "acknowledged" : true, "insertedId" : ObjectId("5e960080ed011c280a0905c9") } > db.demo602.insertOne({id:2, Name:"David"});{ "acknowledged" : true, "insertedId" : ObjectId("5e960086ed011c280a0905ca") } > db.demo602.insertOne({id:1, Name:"Bob"});{ "acknowledged" : true, "insertedId" : ObjectId("5e96008ced011c280a0905cb") } > db.demo602.insertOne({id:3, Name:"Mike"});{ "acknowledged" : true, "insertedId" : ObjectId("5e960092ed011c280a0905cc") } > db.demo602.insertOne({id:2, Name:"John"});{ "acknowledged" : true, "insertedId" : ObjectId("5e960099ed011c280a0905cd") } > db.demo602.insertOne({id:1, Name:"Sam"});{ "acknowledged" : true, "insertedId" : ObjectId("5e9600a1ed011c280a0905ce") }Display all documents from a collection with the help of find() method −> db.demo602.find();This will produce the following ...
Read MoreUpdate in MongoDB and prevent overwrite?
Let us create a collection with documents −> db.demo601.insertOne( ... { ... id:1, ... userDetails: ... { ... userName:"John", ... userMailId:"John@gmail.com" ... } ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e95ff5ced011c280a0905c7") } > > db.demo601.insertOne( { id:2, userDetails: { userName:"Carol", userMailId:"Carol@gmail.com" } } );{ "acknowledged" : true, "insertedId" : ObjectId("5e95ff71ed011c280a0905c8") }Display all documents from a collection with the help of find() method ...
Read MoreCreate a new user and set role in MongoDB
For this, use userAdminAnyDatabase since it gives all permission like admin. Following is the syntax −use admin db.createUser( { user: "yourUserName", pwd: "yourPassword", roles: [ { role: "yourRoleName", db: "yourDatabaseName" } ] } )Let us implement the above syntax to create a user role. Following is the query to create a user with role "userAdminAnyDatabase" −> use admin switched to db admin > db.createUser( ... { ... user: "David Miller", ... pwd: "123456", ... roles: [ { role: "userAdminAnyDatabase", db: "admin" } ] ... } ... )This will produce the following output −Successfully added user: { "user" : "David Miller", "roles" : [ { "role" : "userAdminAnyDatabase", "db" : "admin" } ] }
Read MoreHow to use custom variable while updating a MongoDB document?
To update, use update() and following is the syntax to create and use a sample custom variable −var anyVariableName=yourValue; db.yourCollectionName.update({filter}, {$set:{yourFieldName:yourVariableName}});Let us create a collection with documents −> db.demo600.insertOne({id:1, Name:"Robert"});{ "acknowledged" : true, "insertedId" : ObjectId("5e94a063f5f1e70e134e2699") } > db.demo600.insertOne({id:2, Name:"Mike"});{ "acknowledged" : true, "insertedId" : ObjectId("5e94a06bf5f1e70e134e269a") } > db.demo600.insertOne({id:3, Name:"Sam"});{ "acknowledged" : true, "insertedId" : ObjectId("5e94a072f5f1e70e134e269b") }Display all documents from a collection with the help of find() method −> db.demo600.find();This will produce the following output −{ "_id" : ObjectId("5e94a063f5f1e70e134e2699"), "id" : 1, "Name" : "Robert" } { "_id" : ObjectId("5e94a06bf5f1e70e134e269a"), "id" : 2, "Name" : "Mike" } ...
Read MoreHow to subtract values (TotalPrice – Discount) from document field values in MongoDB?
To subtract values from document field values, use $subtract in MongoDB aggregate(). Let us create a collection with documents −> db.demo599.insertOne({"TotalPrice":250, "DiscountPrice":35});{ "acknowledged" : true, "insertedId" : ObjectId("5e948192f5f1e70e134e2696") } > db.demo599.insertOne({"TotalPrice":400, "DiscountPrice":10});{ "acknowledged" : true, "insertedId" : ObjectId("5e948199f5f1e70e134e2697") } > db.demo599.insertOne({"TotalPrice":1550, "DiscountPrice":50});{ "acknowledged" : true, "insertedId" : ObjectId("5e9481a0f5f1e70e134e2698") }Display all documents from a collection with the help of find() method −> db.demo599.find();This will produce the following output −{ "_id" : ObjectId("5e948192f5f1e70e134e2696"), "TotalPrice" : 250, "DiscountPrice" : 35 } { "_id" : ObjectId("5e948199f5f1e70e134e2697"), "TotalPrice" : 400, "DiscountPrice" : 10 } { "_id" : ObjectId("5e9481a0f5f1e70e134e2698"), "TotalPrice" : 1550, "DiscountPrice" ...
Read MoreFind which MongoDB document contains a specific string?
To find which document contains a specific string, use $regex along with find(). Let us create a collection with documents −> db.demo597.insertOne({"Name":"John Doe"});{ "acknowledged" : true, "insertedId" : ObjectId("5e947ae3f5f1e70e134e2690") } > db.demo597.insertOne({"Name":"John Smith"});{ "acknowledged" : true, "insertedId" : ObjectId("5e947ae8f5f1e70e134e2691") } > db.demo597.insertOne({"Name":"Chris Brown"});{ "acknowledged" : true, "insertedId" : ObjectId("5e947aeff5f1e70e134e2692") } > db.demo597.insertOne({"Name":"Adam Smith"});{ "acknowledged" : true, "insertedId" : ObjectId("5e947afff5f1e70e134e2693") }Display all documents from a collection with the help of find() method −> db.demo597.find();This will produce the following output −{ "_id" : ObjectId("5e947ae3f5f1e70e134e2690"), "Name" : "John Doe" } { "_id" : ObjectId("5e947ae8f5f1e70e134e2691"), "Name" : "John Smith" } ...
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