MongoDB

MongoDB working notes: collections, JSON vs BSON, and CRUD operations with their shell commands.

1. Collections

• show collections → To list collections
• db.customer.insertOne({"name":"Ram"}) → Implicit creation
• db.createCollection("customers") → Explicit Creation
• db.createCollection(nameOfCollection, options) → Syntax
• options → {capped: true} if true, need to give size.
• {size: 34234} in bytes
• {autoIndexId: true} If true, _id will be indexed
• {max:100} max 100 docs in a collections for capped collection
• db.customers.drop() To drop/delete the collection

2. JSON vs BSON

3. CRUD - Operations

a. Create

• syntax → db.customers.insertOne(jsonDocument,options) This will insert one document in the collection.
• db.customers.insertMany(ArrayOfJsonDocuments, options) This will insert all the documents in the array
• If _id is not provided, mongoDb will give unique UUID. If specified, mongo will use that
• writeConcern option →
• ordered option →

b. Read

• Two ways db.collection.find(filters, options) , db.collection.findOne()
• findOne method gives the first match, and default sorting is based on insertion order, the first inserted will come first
• find → if no filter given, it will return all docs, but in a cursor/iterator
• options → the options can be an object to tell what keys are required. {name:true,_id:false}

c. Update

• updateOne(filter, operatorWithValueTobeUpdated) → Updates first doc that passes the filter.
• Example -db.collection.updateOne({name:"john"}, {$set: {name:"John", age:50}})
• updateMany(filter, OperatorWithUpdateValue) → Updates all the docs which matches the filter

d.