MongoDB

What is mongoDB
Non Relational DB: It means it stores json in
document rather than table.
Schemaless
example:
{“first-name”: “jhon”, “last-name”:”smith”, “age”:32 }
{“first-name”: “jhon”, “last-name”:”smith”, “age”:32 ,
gender:”male”}

Why NoSQL?
Trend shows that NoSQL is used in big data in
real time application.
Some of the key Feature are :
Simple in Design
Supports Horizontal Scaling
Data Availability

NoSQL Database Available
Clusterpoint
Couchbase
CouchDB
MongoDB
etc.

MongoDB doesn’t supports
Joins
Transaction across multiple collections.
But new version supports “Transaction”

Crud operation equivalent to RDBMS
Operations MongoDB RDBMS
Create Insert Insert
Read Find Select
Update Update Update
Delete Remove Delete

Compare terms in NoSQL / RDBMS

MongoDB hasn’t query language
Like SQL, MongoDB has no query language all
operation exists as method or functions

MongoDB Query
db.user.find()
This will get all the data from user collection
db.user.findOne()
It will get the first record from the user
collection

Command
Equivalent to where clause
db.user.find({“first_name” : “john”})
This will fetch all the data along with all col whose first_name is equal to john
db.user.find({“first_name” : “john”}, {“first_name” : true})
This will only get the first_name as a result set along with _id
db.user.find({“first_name” : “john”}, {“first_name”:true, “_id”: false})
This will exclude _id from the result se

Craeting a dummy data
for(i=0; i<1000;i++) { name = ["john", "smith",
"laura"]; for(j=0;j<3;j++){ db.student.insert
({"student_id": i, "stu_name":name[j], "score":
Math.round(Math.random()*100)}) } };

And in where clause
db.student.find({"stu_name":"smith", "score":90});
This will fetch all the records which have stu_name = smith and score=90
db.student.find({"stu_name":"smith", "score":90}, {"stu_name":true});
This will fetch all the records which have stu_name = smith and score=90 but
return only stu_name along with _id
Greater than Operator
command

Where clauses (< , >)
$gt , $gte, $lt and $lte Operator
db.student.find({"stu_name":"smith", "score": { $gt : 95}}, {"stu_name":true,
score:true});
Fetch the data whose score is greater than 95
db.student.find({"stu_name":"smith", "score": { $gt : 95, $lt : 98}}, {"stu_name":
true, score:true});
Fetch the data whose score is greater than 95 but less than 98

OR operator
db.student.find({$or: [{"score":90}, {"score" :
80}]});
This will fetch the data whose score is either 90
or 80.

Nature of polymorphism
db.student.find({"stu_name" : {$lt : "l"}, "score" : {$gt : 98}})
This will fetch the student name less than “l”
db.student.find({"stu_name" : {$lt : 30}})
Note : tightly bound within the data type

Command [Regex , exists, type ]
db.student.find({"stu_name" : {$regex : "ih"}})
db.student.find({"stu_name" : {$exists : true}})
db.student.find({"stu_name" : {$type : 1}})
It will fetch the data of number type
db.student.find({"stu_name" : {$type : 2}})
It will fetch the data of string type

Seach in Array
db.student.insert({"stu_name" : 11, "subject" :["hindi", "english", "math"]})
db.student.insert({"stu_name" : 22, "subject" :["math", "german", "spanish"]})
db.student.insert({"stu_name" : 22, "subject" :["math", "german", 100]})
db.student.find({"subject" : "hindi"})
db.student.find({"subject" : 100})
(Another type of polymorphism)

Continue...
db.student.find({"subject" : {$all : ["hindi", "english" ]}})
Fetch the data which contains both in subject array
db.student.find({"subject" : {$in : ["hindi", "math" ]}})
Return the data set which satisfy either of the value

Cursor
>cur = db.student.find({"subject" : {$in : ["hindi", "math" ]}}), null;
null
> cur.hasNext()
true
> cur.next()
{
"_id" : ObjectId("54421c362d3b0ea3d1c08eb2"),
"stu_name" : 11,
"subject" : [
"hindi",
"english",
"math"
]
}

count the number of document
> cur = db.student.find({"subject" : {$in : ["hindi", "math" ]}});
{ "_id" : ObjectId("54421c362d3b0ea3d1c08eb2"), "stu_name" : 11, "subject" : [
"hindi", "english", "math" ] }
"math", "german", "spanish" ] }
"math", "german", 100 ] }
> cur = db.student.count({"subject" : {$in : ["hindi", "math" ]}});
3
>

Aggregation
Simple GroupBy Clause
URL : https://www.youtube.com/watch?
v=3lEpnMcfpCs

Command
Count
> db.student.aggregate([ {$group: { _id: "$stu_name", num_student: {$sum : 1}}}])
{
"result" : [
{
"_id" : 22,
"num_student" : 2
},
{
"_id" : 40,
"num_student" : 1
},
{
"_id" : 30,
"num_student" : 1

Sum with group
SUM on Score
> db.student.aggregate([ {$group: { _id: "$stu_name", num_student: {$sum : “$score”}}}])
Sort on score :
db.student.aggregate([ {$group: { _id: "$stu_name", num_student1: {$sum : "$score"}}}, {$sort :
{num_student1 : 1}}])
db.student.aggregate( {$match : {"stu_name" : "smith"}}, { $group: {_id : "$stu_name" , total : {$sum :
1}}} )
> db.student.aggregate([ {$group: { _id: "$stu_name", num_student: {$sum : “$score”}}}], {explain :

Thanks You
Special Thanks To ICREON.
Your custom link is:
http://webchat.freenode.net?channels=python-dilli-meetup-group&uio=d4
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MongoDB

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MongoDB