MongoDB Basic Commands

To start the server:
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Go to -> command promt -> set the path till bin
ex:
C:\mongodb-win32-i386-2.6.4\bin
then -> mongod --dbpath C:\mongodb-win32-i386-2.6.4\bin
the server will start running

create db & select a db
-----------------------
use tommy

create collections
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use tommy - select the db
db.createCollection("employees")

create collections and insert the data
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db.employees.insert({"id":111,"name":"tom"})

view the list of dbs
---------------------
show dbs

view the list of collections(tables)
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show collections

view the records in the collections
-----------------------------------
db.employees.find()

Delete a collection
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db.employees.drop() - to delete the collection
db.employees.remove() - remove all the records from the collection

Delete a speciic doc from the collection
-----------------------------------------
>db.employees.remove({name:"tom"})
>db.employees.remove({name:"tom"},1) - will delete oly one record

to view the current db
-----------------------
db

delete a db
-------------
use tommy - select a db
db.dropDatabase()

note
-----
>in mongodb you dont need to create collections.
>it creates collections automatically, when you insert some documents

insert multiple documents in a single query
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db.employees.insert([{ },{ }])

to display the results in a formatted way
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db.employees.find().pretty()

update
---------
db.employees.update({name:'tomfree'},{$set:{name:'tomm'}})
>db.employee.update({id:111},{$set:{desig:'sr manager'}})
>db.employee.update({"_id" : ObjectId("529589614eff477245718bdc")},{$set:{email:'cristina@gmail.com'}})
- to add an extra field

to update multiple docs
------------------------
db.employees.update({name:'tomfree'},{$set:{name:'tomm'}},{multi:true})

to update multiple docs - with options
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db.your_collection.update({},{$set : {"new_field":1}},false,true)

db.your_collection.update({},{$set : {"new_field":1}},{upsert:false,multi:true})

Note:
-----

-> In the above example last 2 fields false, true specifies the upsert and multi flags.

Upsert: If set to true, creates a new document when no document matches the query criteria.

Multi: If set to true, updates multiple documents that meet the query criteria. If set to false, updates one document.

-> This is for Mongo versions prior to 2.2. For latest versions the query is changed a bit

to get the sum of the single field:
-----------------------------------
db.Gits_OpenClose.aggregate({$match:{"Year": 2014,"Month": 1}},{$group:{_id: null,total:{$sum:"$Opened"}}})

to update the existing collections with other datas
-----------------------------------------------------
db.employees.save({_id: ObjectId("52945e82e2c023a457cf152e"),name:'tom',id:1111})
>this s by using object_id

to find a specific column
----------------------------
db.employees.find({},{oth:1,_id:0})
>oth - column name
>1 - used to show the specific field
>0 - not to show
>_id:0 - to hide the object id

to limit the records:
----------------------
db.employees.find({},{oth:1,_id:0}).limit(2)

skip method:
------------
db.employees.find({},{oth:1,_id:0}).limit(1).skip(1)
>the default value of skip method is 0.

Sorting:
--------
db.employees.find({},{oth:1,_id:0}).sort({'oth':1})
>1 - ascending
>-1 - descending
db.data.find({},{'Org From Date':''}).sort({'Org From Date':-1}).limit(50)

update:
-------
>db.Employee.update({"_id" : ObjectId("529489e1f2e76698bd1c1616")}, {$set: {"Skill.Sports": "Cricket"}});
>db.Employee.update({_id: ObjectId("529489e1f2e76698bd1c1616")}, {$set: {'Skills.tech':['nosql','java']}});

where conditions
-----------------
>db.employee.find({gender:'f'}) - where gender=f
>db.employee.find({salary:{$gt:50000}}) - where salary>50000
>db.employee.find({salary:{$gt:50000}},{name:1,desig:1,_id:0}) - select name,desig from employee where salary>50000

Indexing
----------
db.employee.ensureIndex({'id':1})
>1 - creating index in ascending order
>2 - creating index in descending order

Aggrigation
------------
db.employee.aggregate([{$group : {_id : "$id", num_tutorial : {$sum : 1}}}])

aggrigation - where
--------------------
db.employee.aggregate([{$match:{salary:{$gt:50000}}},{$group : {_id : "$gender", num_tutorial : {$sum : 1}}}])

Aggre - operations
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count - db.employee.count() - table total count
count - db.employee.count({city:'blore'}) - count of city which is blore
distinct - db.employee.distinct('city')
db.test.count({sports:'football,hockey'},{name:'',sports:''})

in
---
db.case_tbl.find( { empid: { $in: [ 96761, 95939 ] } } )
db.employee.find({id:{$in:[111,222,333]}},{name:'',desig:'',_id:0})

skip() - if wanna skip first 2 docs
-----------------------------------
db.employee.find().skip(2)

total sum:
-----------
db.procount.aggregate({$group:{_id:null,total:{$sum:'$ProCount'}}})

important
----------
db.Employee.find({ "Contact.ZipCode" : "600071"},{"Contact.Address":1})

aggregate:
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db.employee.aggregate({$group:{_id:'$city',total_count:{$sum:1},max_salary:{$max:'$salary'},
min_salary:{$min:'$salary'},avg_salary:{$avg:'$salary'}}})

multiple group:
-----------------
db.employee.aggregate([{$group:{_id:{city:'$city',Design:'$desig'},count:{$sum:1}}}])

var a=db.employee.aggregate([{$group:{_id:{city:'$city',design:'$desig'},count:{$sum:1}}}])
printjson(a)

to insert multiple records:
----------------------------
for(var i=1;i<=10;i++)db.test.insert({id:111,name:'tom',desig:'ase',salary:5000})

import csv to mongodb
----------------------
mongoimport --host localhost --db test --collection data --type csv --file Emp_Data.csv --headerline

distinct count
---------------
db.data.distinct('Emp NO').length

OR:
---
db.emp1.aggregate(
  {$match:{$or:[{"DOE.YEAR":null},{"DOE.YEAR":2013}],"DOJ.YEAR":{$lte : 2013}}},
  {$group:{_id:{},
   count:{ $sum:1}}})

some operators:
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$cmp - compare
$eq - equal
$gt - greater than
$gte - greater than or eequal to
$lt - less than
$lte - less than or equal to
$ne - not equal to