MongoDB

Friends, After MongoDB basic overview and system setup now let’s discuss some basic CRUD operations on MongoDB.

First start MongoDB service which we installed in previous article using below command. You can change the db and log path as per your convenience –

Step-1 : Install service

>mongod –dbpath D:\MongoDbFiles\data –logpath “D:\MongoDbFiles\logs\mongo.logs” –logappend –install –serviceName mdb27017 –serviceDisplayName “MongoDB Server Instance 27017” -serviceDescription “MongoDB Server Instance running on 27017”

Step-2 : Start Service

>net start mdb27017

Step-3 : Start mongo client/shell

>mongo OR mongo.exe

As we have three things in MongoDB which are Database, Collection and Document. So lets do some CRUD operation on these.

CRUD Operations on Database (In MongoDB, databases hold collections of documents) –

Create => use DATABASE_NAME command will create a new database if it doesn’t exist, otherwise it will switch to the existing database.
- > use TestDB
- switched to db TestDB
Read => db command is use to display current database name and show dbs use to display all database names. If a database database does not have any record then it will not display in the list.
- > db
- TestDB
- > show dbs
- admin 0.00 GB
  local 0.00 GB
Update => We have two options to rename a database. First, copy database with the new name using db.copyDatabase() method and second is create a backup of database using mongodump utility program and restore with a new name using mongorestore utility and then delete the old database. Make sure that new database is created before deleting old database.
- Rename with Database Copy
  - > db.copyDatabase(‘old_database_name’, ‘new_database_name’)
  - { “ok” : 1 }
- Rename with Backup/Restore
  - Backup => mongodump is a utility for creating a binary export of the contents of a database. Since its a program not command so we have to run it from the system command prompt, not the mongo shell.
  - > mongodump –db TestDB
  - Restore => mongorestore program writes data from a binary database dump created by mongodump to a MongoDB instance. Since its also a program not command so we have to run it from the system command prompt, not the mongo shell.
  - > mongorestore –db NewTestDatabase ./dump/TestDB
Delete => db.dropDatabase() is used to drop the current database.
- > db.dropDatabase()
- { “dropped” : “TestDB”, “ok” : 1 }

CRUD Operations on MongoDB Collections (Collections are analogous to tables in relational databases and stores documents)-

Create – There are two ways to create collections-
- Implicit Creation – MongoDB also creates the collection when you first store data for that collection i.e If the collection does not exist, insert operations will create the collection automaticaly.
  - > db.myNewCollection.insertOne({A:10})
  - {
    “acknowledged” : true,
    “insertedId” : ObjectId(“59b82dae3deeaa1a93747b62”)
    }
  - > db.myNewCollection2.createIndex({B:10})
  - {
    “createdCollectionAutomatically” : true,
    “numIndexesBefore” : 1,
    “numIndexesAfter” : 2,
    “ok” : 1
    }
- Explicit Creation –
  - MongoDB provides the db.createCollection() method to explicitly create a collection with various options, such as setting the maximum size or the documentation validation rules.
  - > db.createCollection(“myExplicitCollection2”, { capped : true, size : 6142800, max : 10000 } )
  - { “ok” : 1 }
Read – show command is used to display all available collections
- > show collections
- impCollection
  myExplicitCollection
Update – db.COLLECTION_NAME.renameCollection(target, dropTarget) is use to update the collection name
- > db.myNewCollection.renameCollection(“myNewRenamedCollection”, true)
- { “ok” : 1 }
Delete – db.COLLECTION_NAME.drop() is use to delete a collection
- > db.myNewCollection.drop()
- true

CRUD Operations on MongoDB Documents (MongoDB documents is a set of key-value pairs and basic unit of data LIKE row in the RDBMS) –

Create – Below are some methods to create documents
- db.COLLECTION_NAME.insert(<document or array of documents>) – It allows you to insert One or more documents in the collection and Returns a WriteResult object
  - > db.testCollection.insert({a:10})
    WriteResult({ “nInserted” : 1 })
  - In the inserted document, if we don’t specify the _id parameter, then MongoDB assigns a unique ObjectId for this document
  - deprecated in major driver
- db.COLLECTION_NAME.insertOne(document) – It allows you to insert exactly 1 document in the collection and returns the document.
  - > db.testCollection.insertOne({ _id: 10, name: “jogendra”})
    { “acknowledged” : true, “insertedId” : 10 }
- db.COLLECTION_NAME.insertMany() – It allows you to insert an array of documents in the collection
  - > db.testCollection.insertMany([{ _id: 1, name: “jogendra”},{name: “anmol”}])
  - {
    “acknowledged” : true,
    “insertedIds” : [
    1,
    ObjectId(“59b97fbf6edbc77428869950”)
    ]
    }
- db.COLLECTION_NAME.save()
  - > db.testCollection.save({ name :”sahib”, age : 4.5})
Read –
1. Select All Documents in a Collection.
  - >db.COLLECTION_NAME.find(query, projection)
    - query – Optional. Specifies selection filter
    - projection – Optional. Specifies the fields to return in the documents that match the query filter. To return all fields in the matching documents, omit this parameter
  - >db.testCollection.find({}) OR db.testCollection.find()
    { “_id” : 1, “name” : “jogendra”, “age” : 30 }
    { “_id” : 2, “name” : “anmol”, “age” : 5 }
    { “_id” : 3, “name” : “bani”, “age” : 5 }
  - To display the results in a formatted way, you can use pretty() method
2. Return only Selected Fields- We need to pass in the second parameter i.e projection for required fields only. _id fields always returns if not explicitly excluded.
  - db.testCollection.find({ age : 5}, {_id:false, name : true})
  - { “name” : “anmol” }
    { “name” : “bani” }
3. Select one document in a Collection
  - db.COLLECTION_NAME.findOne(query, projection)
    - Without query returns the first document from the collection
      - db.testCollection.findOne()
      - { “_id” : 1, “name” : “jogendra”, “age” : 30 }
    - With a Query Specification returns the first matching document from the bios collection.
      - db.testCollection.findOne({age:5})
      - { “_id” : 2, “name” : “anmol”, “age” : 5 }
4. RDBMS Where Clause Equivalents in MongoDB – All operations are on below documents-
  { “_id” : 1, “name” : “jogendra”, “age” : 30 }
  { “_id” : 2, “name” : “anmol”, “age” : 5 }
  { “_id” : 3, “name” : “bani”, “age” : 5 }
  - Equality (=)
    - Syntax- {:}
    - Ex- Select all documents where age=5
    - > db.testCollection.find({age:5})
    - { “_id” : 2, “name” : “anmol”, “age” : 5 }
      { “_id” : 3, “name” : “bani”, “age” : 5 }
  - Less Than (<)
    - Syntax- {:{$lt:}}
    - Ex- Select all documents where age < 5
    - > db.testCollection.find({age:{$lt:50}})
    - { “_id” : 1, “name” : “jogendra”, “age” : 30 }
      { “_id” : 2, “name” : “anmol”, “age” : 5 }
      { “_id” : 3, “name” : “bani”, “age” : 5 }
  - Less Than Equals (<=)
    - Syntax- {:{$lte:}}
    - > db.testCollection.find({age:{$lte:5}})
    - { “_id” : 2, “name” : “anmol”, “age” : 5 }
      { “_id” : 3, “name” : “bani”, “age” : 5 }
  - Greater Than ( > )
    - Syntax – {:{$gt:}}
    - > db.testCollection.find({age:{$gt:5}})
    - “_id” : 1, “name” : “jogendra”, “age” : 30 }
  - Greater Than Equals ( >= )
    - Syntax – {:{$gte:}}
    - > db.testCollection.find({age:{$gte:30}})
    - { “_id” : 1, “name” : “jogendra”, “age” : 30 }
  - Not Equals ( != )
    - Syntax – {:{$ne:}}
    - db.testCollection.find({age:{$ne:30}})
    - { “_id” : 2, “name” : “anmol”, “age” : 5 }
      { “_id” : 3, “name” : “bani”, “age” : 5 }
  - Like (%text%)
    - name like ‘%o%’ => contains [ / o /]
      - > db.testCollection.find({name : /o/})
    - name like ‘j%’ => start with [ / ^ J / ]
      - > db.testCollection.find({name : / ^j /})
    - name like ‘%j’ => end with [ / i $/ ]
      - > db.testCollection.find({name : /i$/})
5. AND in MongoDB ($and )- In the find() method, if you pass multiple keys in a array then MongoDB treats it as AND condition
  - Syntax – >
    db.testCollection.find( { $and: [ {key1: value1}, {key2:value2}] })
  - > db.testCollection.find({$and : [{age:5}, {name:”anmol”}]})
  - { “_id” : 2, “name” : “anmol”, “age” : 5 }
6. OR in MongoDB ( $or )
  - db.testCollection.find( { $or: [ {key1: value1}, {key2:value2}] })
  - > db.testCollection.find({ $or : [{age:30}, {name : “anmol” }]})
  - { “_id” : 1, “name” : “jogendra”, “age” : 30 }
    { “_id” : 2, “name” : “anmol”, “age” : 5 }
7. Using AND and OR Together
  - Ex- where age <= 50 AND (name = “Jogendra” OR name = “bani”)
  - > db.testCollection.find({ age:{$lte:50}, $or:[{name :”jogendra”} , {name : “bani” }]})
  - { “_id” : 1, “name” : “jogendra”, “age” : 30 }
    { “_id” : 3, “name” : “bani”, “age” : 5 }
Update –
- Update a Single Document-
  - db.collection.updateOne(filter, update, options)
    - Updates a single document within the collection based on the filter.
    - > db.testCollection.updateOne({_id:1}, {$set: {name:”Jogendra Singh”, age : 31}})
    - { “acknowledged” : true, “matchedCount” : 1, “modifiedCount” : 1 }
    - > db.testCollection.updateOne({_id:1}, {$set: {name:”Jogendra Singh”, age : 31}, $currentDate: { lastModified: true }})
    - { “_id” : 1, “name” : “Jogendra Singh”, “age” : 31, “lastModified” : ISODate(“2017-09-14T19:16:31.167Z”) }
    - $set – to update the value of the field
    - $currentDate – to update the value of the lastModified field to the current date
  - db.collection.update(query, update, options)
    - Either updates or replaces a single document that match a specified filter or updates all documents that match a specified filter.
- Update Multiple Documents
  - db.collection.updateMany(filter, update, options)
    - Updates multiple documents within the collection based on the filter.
    - db.testCollection.updateMany({ $or: [{name:”bani”},{name : “anmol”}]}, { $set : {class: “LKG”}})
    - { “_id” : 2, “name” : “anmol”, “age” : 5, “class” : “LKG” }
      { “_id” : 3, “name” : “bani”, “age” : 5, “class” : “LKG” }
    - db.testCollection.updateMany({ age : {$lt: 30} }, { $set : {city : “Delhi”} })
    - { “_id” : 2, “name” : “anmol”, “age” : 5, “class” : “LKG”, “city” : “Delhi” }
      { “_id” : 3, “name” : “bani”, “age” : 5, “class” : “LKG”, “city” : “Delhi” }
- Replace a Document
  - db.collection.replaceOne(filter, replacement, options)
    - Replaces a single document within the collection based on the filter.
    - To replace the entire content of a document except for the _id field, pass an entirely new document as the second argument to db.collection.replaceOne()
    - db.testCollection.replaceOne({“_id” : 3}, { firstname : “Gurbani”, lastname : “kaur”, age : 2.5})
    - { “_id” : 3, “firstname” : “Gurbani”, “lastname” : “kaur”, “age” : 2.5 }
- Rename field name
  - $rename
    - The $rename operator updates the name of a field
    - db.testCollection.update({“_id”: 3}, {$rename : {firstname : “First-Name”}})
    - { “_id” : 3, “lastname” : “kaur”, “age” : 2.5, “First-Name” : “Gurbani” }
Delete –
- db.collection.remove()
  - Removes documents from a collection.
  - he db.collection.remove() method can have one of two syntaxes. The remove() method can take a query document and an optional justOne boolean.
  - >db.testCollection.remove({“_id” : ObjectId(“59b992326edbc77428869952”)})
- db.collection.deleteOne(filter, { writeConcern: , collation: })
  - > db.testCollection.deleteOne({$and : [{name:”sahib”},{age:4.5}]})
  - { “acknowledged” : true, “deletedCount” : 1 }
- db.collection.deleteMany(, { writeConcern: , collation: })
  - Delete all documents that match a specified filter.
  - > db.testCollection.deleteMany({age : {$gte : 50}})

https://docs.mongodb.com/manual/reference/method/

Programming is Easy…

MongoDB is an open-source document database that provides high performance, high availability, and automatic scaling.

MongoDB stores data in flexible BSON documents meaning fields can vary from document to document and data structure can be changed over time. BSON is a binary representation of JSON documents, though it contains more data types than JSON.

Let’s understand the terms used in MongoDB-

Database –
- A database is an organized collection of data.
- A physical container for collections. Each database gets its own set of files on the file system.
- MongoDB databases hold collections of documents.
Collection –
- Collection is a group of MongoDB documents.
- It is the equivalent of an RDBMS table. A collection exists within a single database.
- Collections do not enforce a schema. Documents within a collection can have different fields. Typically, all documents in a collection are of similar or related purpose.
- MongoDB collections hold data records i.e BSON documents.
Documents –
- A record in a MongoDB collection.
- Documents are analogous to JSON objects(but exist in the database in a more type-rich format known as BSON).
- MongoDB stores data records as BSON documents. BSON is a binary representation of JSON documents, though it contains more data types than JSON
- Documents have dynamic schema means that documents in the same collection do not need to have the same set of fields or structure, and common fields in a collection’s documents may hold different types of data.
- MongoDB documents is a set of key-value pairs and basic unit of data.

mongo

Components ?

Mongo.exe => The mongo shell is an interactive JavaScript interface to MongoDB and is a component of the MongoDB package. You can use the mongo shell to query and update data as well as perform administrative operations. we can start the mongo shell by using the mongo command in the command prompt.

Features ?

High Performance – MongoDB provides high performance data persistence. In particular-
- Support for embedded data models reduces I/O activity on database system.
- Indexes support faster queries and can include keys from embedded documents and arrays. Rich Query Language
Rich Query Language – MongoDB supports a rich query language to support read and write operations (CRUD) as well as:
- Data Aggregation
- Text Search and Geospatial Queries.
High Availability – MongoDB’s replication facility, called replica set(A replica set is a group of MongoDB servers that maintain the same data set, providing redundancy and increasing data availability.), provides:
- automatic failover and
- data redundancy.
Horizontal Scalability – MongoDB provides horizontal scalability as part of its core functionality:
- Sharding distributes data across a cluster of machines.
- MongoDB 3.4 supports creating zones of data based on the shard key. In a balanced cluster, MongoDB directs reads and writes covered by a zone only to those shards inside the zone. See the Zones manual page for more information.
Support for Multiple Storage Engines – MongoDB supports multiple storage engines, such as:
- WiredTiger Storage Engine
- MMAPv1 Storage Engine.

Environment Setup-

Download and Install latest version from – https://docs.mongodb.com/manual/installation/
- Let’s assume default installation directory is – C:\Program Files\MongoDB\Server\3.4\bin
Set Env Path variable to – C:\Program Files\MongoDB\Server\3.4\bin
- Now check the version using below command to ensure that path is setup correctly- C:\Users\jogen>mongo -version
MongoDB requires a data folder to store its files. The default location for the MongoDB data directory is “C:\data\db”
If you want to store the data files at different location so we can set the preferred location path using –dbpath as below then it will show waiting for connections message on the console output, which indicates that the mongod.exe process is running successfully. If this path contains spaces then put all its path in double qoutes.
- C:\Users\jogen>mongod –dbpath “D:\MongoDbFiles\data”
Set log path – used by mongo daemon process,for flush out logs instead of in standard console as-
- C:\Users\jogen>mongod –logpath “D:\MongoDbFiles\logs\mongo.logs” –logappend
Set port using –port, default is- 27017

We can also specify above configuration option using a config file. Config file is just text file, containing the parameters in the key=value form and each one is specified on the every line of file. We basically provide file path (which contains the configurations) as command line option as “-f” or “–config” as below-

mongo2

C:\Users\jogen>mongod –f D:\Servers\mongodb\config\mongodb.conf
C:\Users\jogen>mongod –config D:\Servers\mongodb\config\mongodb.conf

Start/Stop MongoDB using the Windows services –

MongoDB also comes with excellent support to turn your MongoDB server into a windows service that gets launched automatically at startup.

–install : command line switch to install the service
–remove : command line switch to remove the service
–serviceName : the name for mongod windows service and must adhere to naming services in windows like only accepting the alphanumeric chars with no spaces
–serviceDisplayName : Display name for service that is shown in services console, put this in double quotes if contains the spaces
–serviceDescription : Small description about service, put this in double quotes if contains the spaces

To do this open command prompt with admin rights and fire below on the shell-

mongod –dbpath “D:\MongoDbFiles\data” –logpath “D:\MongoDbFiles\logs\mongo.logs” –logappend –install –serviceName mdb27017 –serviceDisplayName “MongoDB Server Instance 27017” –serviceDescription “MongoDB Server Instance running on 27017”

In log path specified, you can check for the whether windows services started or not or look into services.msc for –

GUI tool for MongoDB –

Robo 3T (formerly Robomongo) is the free lightweight GUI for MongoDB enthusiasts.

https://robomongo.org/

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Programming is Easy…

MongoDB Basics – Part 2 (CRUD Operations)

CRUD Operations on Database (In MongoDB, databases hold collections of documents) –

CRUD Operations on MongoDB Collections (Collections are analogous to tables in relational databases and stores documents)-

CRUD Operations on MongoDB Documents (MongoDB documents is a set of key-value pairs and basic unit of data LIKE row in the RDBMS) –

Programming is Easy…

MongoDB Basics – Part 1

Components ?

Features ?

Environment Setup-

Start/Stop MongoDB using the Windows services –

GUI tool for MongoDB –

Programming is Easy…

CRUD Operations on Database (In MongoDB, databases hold collections of documents) –

CRUD Operations on MongoDB Collections (Collections are analogous to tables in relational databases and stores documents)-

CRUD Operations on MongoDB Documents (MongoDB documents is a set of key-value pairs and basic unit of data LIKE row in the RDBMS) –

Programming is Easy…

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Components ?

Features ?

Environment Setup-

Start/Stop MongoDB using the Windows services –

GUI tool for MongoDB –

Programming is Easy…

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