This document provides an overview of MongoDB administration commands and CRUD operations. It discusses how to select databases, show collections, import/export data, and perform basic CRUD operations like insert, find, update, and remove in MongoDB. It also covers additional find methods like logical operators, array operations, and accessing embedded documents. Methods for updating include $set, $inc, $unset, and multi updates.

1. MongoDB 102

2. Session II Topics
• Basic MongoDB administration commands
• CRUD operations in MongoDB
• Data creation in MongoDB
• Reading data in MongoDB
• Updating data in MongoDB
• Removing data in MongoDB

3. Basic MongoDB Administration
Commands
Select a database: use database_name
Show databases: show dbs
Drop current database: db.dropDatabase()
Get current database name: db.getName()
Show all collections of current db: show collections
Drop collection: db.collection.drop()
Show all indexes on collection: db.collection.getIndexes()
Dump data from MongoDB:
mongodump --db database –c collection_name path_to_dump
Restore data to MongoDB:
mongorestore –-db database –c collection_name path_of_dump_file
Export data from MongoDB:
mongoexport –-db database –c collection –-out file_name.json
Import data in MongoDB:
mongoimport –-db database –c collection –-file file_name.json

4. CRUD in MongoDB
Operation MongoDB SQL
Create Insert Insert
Read Find Select
Update Update Update
Delete Remove Delete
MongoDB’s CRUD operations exist as methods/functions in programming languages, not
as a separate query language like SQL.
Language drivers
Mongo Shell (Javascript)
Wire Protocol

5. Data creation in MongoDB
How: db.collection_name.insert(document)
What it does
• Creates a collection if it doesn’t exist
• Inserts document into the collection
_id Field
• Inserts automatically a unique ObjectId, if no unique id specified in the document
• Is unique within the collection
• Comprises of the current time + identifier of the machine + process ID +
process specific local counter
Examples:
db.products.insert({ “item”: “card”, qty : 15})
//Inserting with id
db.products.insert({ _id: 10, “item”: "box", qty: 20 })

6. Reading data in MongoDB
How: db.collection_name.find(query)
db.scores.find() – Find all documents in scores collection
db.scores.findOne() – Find one document randomly
Equality Condition (= where clause)
db.scores.find({ “type” : “exam” })
Limiting which fields to display
db.scores.find({},{ student : 1, _id : 0 })
Comparison operators:
$gt, $gte, $lt, $lte, $ne
db.scores.find({score : { $gt : 60}}) //greater than
db.scores.find({score : { $gte : 60}}) //greater than equal to
db.scores.find({score : { $lt : 60}}) //less than
db.scores.find({score : { $lte : 60}}) //less than equal to
db.scores.find({score : { $ne : 60}}) //not equal to

7. Reading data in MongoDB
How: db.collection_name.find(query)
Logical Operators
AND: db.scores.find({ “type” : “exam”, score : {$gt : 60}})
db.scores.find({ $and : [{ “type” : “exam” },{ score :
$gt : 60}]})
OR: db.scores.find({ $or : [{ “type” : “exam” },{ type : “essay” }]})
NOT: db.scores.find({ score : {$not : { $gt : 60}}})

8. Reading data in MongoDB
How: db.collection_name.find(query)
Finding inside arrays
{ _id: 5, type: "food", item: "aaa", ratings: [ 5, 8, 9 ] }
{ _id: 6, type: "food", item: "bbb", ratings: [ 5, 9 ] }
{ _id: 7, type: "food", item: "ccc", ratings: [ 9, 5, 4 ] }
db.inventory.find({ratings : [5,8,9]}) //exact match on the array
db.inventory.find( { ratings: 5 } ) //find where array contains 5
db.inventory.find( { 'ratings.0': 5 } ) //find where ratings array
contains 5 as the 1st element
db.inventory.find({ratings : {$all :[5, 8]}}) //find where ratings
array contains 5 and 8 both as necessary elements.
db.inventory.find({ratings : {$in :[9, 4]}}) //find where ratings
array contains 5 or 8

9. Reading data in MongoDB
How: db.collection_name.find(query)
Accessing elements using DOT notation
{
"_id" : ObjectId("540cb0e5ff0918e673f1cce9"),
"name" : "Howard Hughes",
"email" : {
"work" : "hhughes@hughes.com",
"personal" : "hhughes@gmail.com"
}
}
db.users.find({"email.work":"hhughes@hughes.com"})

10. Updating data in MongoDB
How: db.collection_name.update(query,update)
db.scores.update({"student":0, "type":"essay"},{ "type":"exam“})})
//Will not really update just the type field. Will Replace the whole
document
db.scores.update({"student":0, "type":"essay"},{ $set :
{"type":"exam“}})})
//Will update only the type field. If the field doesn’t exist will
add it.
db.scores.update({"student":0, "type":"essay"},{ $inc :
{“score":1}})})
//Will increment the score of the student by 1. If field doesn’t exist
Will create the field with value 1
Incrementing a field that has number value
Set

11. Updating data in MongoDB
How: db.collection_name.update(query,update)
db.scores.update({"student":0, "type":"essay"},{ $unset :
{"type": 1}})})
//Will remove the type field from the document
db.scores.update({"student":1000,"type":"exam"},
{$set : { age : 20} },
{ upsert : true })
//Upsert will add a document if it does not exist as per the
Specified query student:1000. Without upsert a normal update will not
add the document if query doesn’t match
//A db.collection.save() is equivalent to update with upsert true, if
The document passed to save contains an _id field
Upsert
Unset

12. Updating data in MongoDB
How: db.collection_name.update(query,update)
db.scores.update({}, { $set : { "title" : "Dr" }} , {multi : true} )
//Will update every document with a title field
//If multi operator is not mentioned, only a single document will
//be updated
Multi update
Update operation can perform 4 operations on a document:
• Wholesale replacement to document
• Manipulate individual fields in a document (update/remove)
• Perform an upsert operation – update / insert
• Update multiple documents

13. Removing data in MongoDB
How: db.collection_name.remove(query)
Remove all documents
db.scores.remove({})
Remove all documents that fulfill a condition
db.scores.remove({ “score” : {$gt : 500}})