MongoDB

Last update: 28 Sep 2022

General info

Comparison between a SQL DBMS and MongoDB

SQL	MongoDB
schema	db
table	collection
record	document

In MongoDB, every document should contain an _id field. Its type is String if manually assigned or ObjectId if assigned by MongoDB.

An URI in srv format:

mongodb+srv://USERNAME:PASSWORD@HOST/DATABASE?options

Command line tools

• mongod : run the server in interactive mode
• mongo : shell client (CLI)
• mongodb-compass: graphical client

Commands

Select the DB that it is created if not existing

use <db>

Show all collections in a db

show collections

Insert one or more documents in a collection

db.<coll>.insertOne ( <document> )
db.<coll>.insertMany ( [ <document1>, <document2>..] )

Insert one or more documents in a collection skipping any error

db.<coll>.insertMany ( [ <document1>, <document2>..], { "ordered":false} )

Query by fields

db.<coll>.find ( {fields} )

Query by fields with projection (1=show the field, 0=hide the field)

db.<coll>.find ( {fields}, {projection})

Query with formatted results

db.<coll>.find ( ... ).pretty()

Count the documents returned by the query

db.<coll>.find ( ... ).count()

Update one document

db.<coll>.updateOne(<selector>, {operators})

Update many document

db.<coll>.updateMany(<selector>, {operators})

Upsert (insert or update)

db.<coll>.upsert

Updates operators:

• scalar: $set, $unset, $min, $max, $inc..
• array: $addToSet, $pop, $popAll, $push, $pull