Skip to main content

MongoDB hello world example


 MongoDB hello world example

mongodb hello world

A quick guide to show you how to do basic operations like create, update, find, delete record and indexing in MongoDB. This example is using MongoDB 2.0.7, running on Mac OS X 10.8, both MongoDB client and server console are run on localhost, same machine.

1. Install MongoDB

Refer to this http://www.mongodb.org/display/DOCS/Quickstart to show you how to install MongoDB on Windows, Linux or Mac. The installation is easy, basically just download the MongoDB zip file, extra and run the command – $MongoDB-folder/bin/mongod.
Uses mongod to start MongoDB.
$./mongod
Tue Sep 11 21:55:36 [initandlisten] MongoDB starting : 
pid=72280 port=27017 dbpath=/data/db/ 64-bit host=Yongs-MacBook-Air.local
Tue Sep 11 21:55:36 [initandlisten] db version v2.0.7, pdfile version 4.5
Tue Sep 11 21:55:36 [initandlisten] options: {}
Tue Sep 11 21:55:36 [initandlisten] journal dir=/data/db/journal
Tue Sep 11 21:55:36 [initandlisten] recover : no journal files present, no recovery needed
Tue Sep 11 21:55:36 [websvr] admin web console waiting for connections on port 28017
Tue Sep 11 21:55:36 [initandlisten] waiting for connections on port 27017

2. Connect MongoDB

To connect MongoDB, uses $MongoDB-folder/bin/mongo
$ ./mongo
MongoDB shell version: 2.0.7
connecting to: test

3. Create a database or table

In MongoDB, both database and table are created automatically when the first time data is inserted. Uses use database-name, to switch to your database (even this is not created yet).
In below example, after you inserted a single record, database “mkyong”, and table “users” are created on the fly.
$ ./mongo
MongoDB shell version: 2.0.7
connecting to: test
> use mkyong
switched to db mkyong
 
> db.users.insert({username:"mkyong",password:"123456"})
> db.users.find()
{ "_id" : ObjectId("504f45cd17f6c778042c3c07"), "username" : "mkyong", "password" : "123456" }
Three database commands you should know.
  1. show dbs – List all databases.
  2. use db_name – Switches to db_name.
  3. show collections – List all tables in the current selected database.
Note
In MongoDB, collection means table in SQL.

4. Insert A Record

To insert a record, uses db.tablename.insert({data}) or db.tablename.save({data}), both works, no idea why MongoDB created both.
> db.users.save({username:"google",password:"google123"})
> db.users.find()
{ "_id" : ObjectId("504f45cd17f6c778042c3c07"), "username" : "mkyong", "password" : "123456" }
{ "_id" : ObjectId("504f48ea17f6c778042c3c0a"), "username" : "google", "password" : "google123" }

5. Update A Record

To update a record, uses db.tablename.update({criteria},{$set: {new value}}). In below example, the password of username : “mkyong” is updated.
> db.users.update({username:"mkyong"},{$set:{password:"hello123"}})
> db.users.find()
{ "_id" : ObjectId("504f48ea17f6c778042c3c0a"), "username" : "google", "password" : "google123" }
{ "_id" : ObjectId("504f45cd17f6c778042c3c07"), "password" : "hello123", "username" : "mkyong" }

6. Find Records

To find or query records, uses db.tablename.find({criteria}).
6.1 List all records from table “users”.
> db.users.find()
{ "_id" : ObjectId("504f48ea17f6c778042c3c0a"), "username" : "google", "password" : "google123" }
{ "_id" : ObjectId("504f45cd17f6c778042c3c07"), "password" : "hello123", "username" : "mkyong" }
6.2 Find records where username is “google”
> db.users.find({username:"google"})
{ "_id" : ObjectId("504f48ea17f6c778042c3c0a"), "username" : "google", "password" : "google123" }

7. Delete Record

To delete a record, uses db.tablename.remove({criteria}). In below example, the record of username “google” is deleted.
> db.users.remove({username:"google"})
> db.users.find()
{ "_id" : ObjectId("504f45cd17f6c778042c3c07"), "password" : "hello123", "username" : "mkyong" }
Note
To delete all records from a table, uses db.tablename.remove().
To drop the table, uses db.tablename.drop().

8. Indexing

Index may help you increase the speed of querying data.
8.1 List all indexes of table “users”, by default the column “_id” is always the primary key and created automatically.
> db.users.getIndexes()
[
 {
  "v" : 1,
  "key" : {
   "_id" : 1
  },
  "ns" : "mkyong.users",
  "name" : "_id_"
 }
]
>
8.2 To create an index, uses db.tablename.ensureIndex(column). In below example, an index is created on column “username”.
> db.users.ensureIndex({username:1})
> db.users.getIndexes()
[
 {
  "v" : 1,
  "key" : {
   "_id" : 1
  },
  "ns" : "mkyong.users",
  "name" : "_id_"
 },
 {
  "v" : 1,
  "key" : {
   "username" : 1
  },
  "ns" : "mkyong.users",
  "name" : "username_1"
 }
]
8.3 To drop an index, uses db.tablename.dropIndex(column). In below example, the index on column “username” is deleted or dropped.
> db.users.dropIndex({username:1})
{ "nIndexesWas" : 2, "ok" : 1 }
> db.users.getIndexes()
[
 {
  "v" : 1,
  "key" : {
   "_id" : 1
  },
  "ns" : "mkyong.users",
  "name" : "_id_"
 }
]
>
8.4 To create an unique index, uses db.tablename.ensureIndex({column},{unique:true}). In below example, an unique index is created on column “username”.
> db.users.ensureIndex({username:1},{unique:true});
> db.users.getIndexes()
[
 {
  "v" : 1,
  "key" : {
   "_id" : 1
  },
  "ns" : "mkyong.users",
  "name" : "_id_"
 },
 {
  "v" : 1,
  "key" : {
   "username" : 1
  },
  "unique" : true,
  "ns" : "mkyong.users",
  "name" : "username_1"
 }
]

10. Help

At last, uses help() to guide you how to do things in MongoDB.
10.1 help – All available commands.
> help
 db.help()                    help on db methods
 db.mycoll.help()             help on collection methods
 rs.help()                    help on replica set methods
 help admin                   administrative help
 help connect                 connecting to a db help
 help keys                    key shortcuts  
 //...
10.2 db.help() – Shows help on db.
> db.help()
DB methods:
 db.addUser(username, password[, readOnly=false])
 db.auth(username, password)
 db.cloneDatabase(fromhost)
 db.commandHelp(name) returns the help for the command
 db.copyDatabase(fromdb, todb, fromhost)
 //...
10.3 db.collection.help() – Shows help on collection (table).
> db.users.help()
DBCollection help
 db.users.find().help() - show DBCursor help
 db.users.count()
 db.users.dataSize()
 db.users.distinct( key ) - eg. db.users.distinct( 'x' )
 db.users.drop() drop the collection
 db.users.dropIndex(name)
 //...
10.4 db.collection.function.help() – Shows help on function.
> db.users.find().help()
find() modifiers
 .sort( {...} )
 .limit( n )
 .skip( n )
 .count() - total # of objects matching query, ignores skip,limit
 .size() - total # of objects cursor would return, honors skip,limit
 .explain([verbose])
    //...







Done. Hope this summary of MongoDB commands could help others.










































Comments








Post a Comment













Popular posts from this blog









Approval Process




















Image







  Salesforce: Approval Process - Who can approve ?       To build an approval workflow in Salesforce is simple, since Salesforce provide  Approval Processes . You can find this under  Setup  -  Create  -  Workflow & Approvals  -  Approval Processes .   In early blogs, we have discussed about  Serial and Parallel Approval  in Salesforce, in this blog, we would like to discuss in depth option of users can approve?   Manager Approval  In the approval process  Step 3. Specify Approver Field and Record Editability Properties , there is option to determine next automated approver.     Notice that  Next Automated Approver Determined By  is not a mandatory field here.   Option available here:   Manager   - a standard field in user object and has no relation with Role Hierarchy  All custom fields in user object with type = Hierarchy - in above sample: Boss and Sales Director.    If you select  Manager  as in above screenshot, when you set up Approval Step, in  Step 3. Select Assigned Approv








Read more










Sending Mass Emails From Salesforce




















Image







  Create a Email Template         Then you either go to the Lead Tab or the Contact Tab and scroll down the page until you see the Mass Email link in the Tools section.     On the first step of the mass email wizard is to create your target list. To do this you have the option of leveraging an existing View that is available on the Leads tab, or you can create a new View from within the wizard. In this example we will create our target list from within the wizard by clicking the   Create New View   link.     In my example I’m   creating a quick View   to grab any Lead that is in the State of California. Notice in Step 2 of the View you can use a Campaign to filter (handy if your Campaign has your target list as Campaign Members!). Remember you have governor limits based on your edition (see paragraph two of this blog posts).     If you’re running Professional Edition for example, and your View pulls more than 250 records, you’ll need to add additional filters to your View to reduce the








Read more










Spring Batch 2.0 -Basic Concepts





















   There is always a healthy debate when talking Java and batches. When I heard  Spring Batch , I had to try it out.  On a previous project, many eons back, I did some batch processing in Java. What hurt me there (after a lots of optimizations) was a call to another persons module. His module happily loaded up an entity bean. You can guess where that ended. Next release I went through the code and replaced the entity bean calls with ONE update SQL statement. That fixed things. I was processing 200k records in 15-20 minutes, with an extremely small memory footprint. Even this I could reduce further if I tuned another module. But the performance was deemed enough and we moved on.   What I personally felt from that experience was the need of a decent Java-based Batch processing framework. Of course having this does not mean use Java for batches. Sometimes for bulk processing doing it in the database may be the right approach.   In this blog I want to go over Spring Batch processing. We wi








Read more