Showing posts with label CRUD. Show all posts
Showing posts with label CRUD. Show all posts

Friday, 4 January 2019

How to Query on MongoDB by _id - INTERMEDIATE II


What if we have to query on MongoDB collections based on the "_id" field, Can we really query on "_id" field ? If so, what is the syntax ? Let's try this out -

Let's first fetch a document's id -

$ db.user.find_one()

{'_id': ObjectId('5c16e863817810ed3fc5e5f9'),
 'Fname': 'atul',
 'Lname': 'Singh',
 'Grade': 12.0,
 'College': 'SGM',
 'Job': 'Student',
 'Address': 'Young St.'}



Now, we will pick the object id and use this to fetch the same document from collection

$ db.user.find_one({'_id':'5c16e863817810ed3fc5e5f9'}) #this will return nothing

$ db.user.find_one({'_id':ObjectId('5c16e863817810ed3fc5e5f9')})
---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
 in 
----> 1 db.user.find_one({'_id':ObjectId('5c16e863817810ed3fc5e5f9')})

NameError: name 'ObjectId' is not defined


We have received this error because ObjectId is not the same as its string representation, it must be converted to ObjectId from a string before it is passed to find command.

$ from bson.objectid import ObjectId
$ db.user.find_one({'_id':ObjectId('5c16e863817810ed3fc5e5f9')})

{'_id': ObjectId('5c16e863817810ed3fc5e5f9'),
 'Fname': 'atul',
 'Lname': 'Singh',
 'Grade': 12.0,
 'College': 'SGM',
 'Job': 'Student',
 'Address': 'Young St.'}



IPYTHON Notebook can be found HERE








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Friday, 28 December 2018

MongoDB with Python - Basics I - CRUD Operations


In Previous few posts (Link), We have learnt about MongoDB Cloud Setup, Installation and Basic commands to do CRUD operation with MongoDB. It can be accessed by programming language such as python, java, and node.js by using respective native drivers. We will start with PyMongo (python driver) to access mongo from python.



CRUD Operation - (Create, Read, Update & Delete) : Link




Next Post on this Series and more on MongoDB can be find here -> LINK





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Friday, 21 December 2018

Learn Mongo DB - Basics #1


While going through old pages, saw these mongoDB posts, so thought of continuing, We have already completed Installation of MongoDB, Now starting off with few basic commands which will help you to play around MongoDB :-)
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Next Post on this Series and more on MongoDB can be find here -> LINK




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