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Basics

Basics​

  • Every cluster consists of replicas
  • Atlas free tier has 3 replicas
  • If any one of them fails, other two still work ensuring reliability
  • Every cluster consists of databases
  • databases consist of collections
  • collections consist of documents
  • cluster → db → collections → documents
  • documents are json like structures with key and value pairs
  • Example:
{
    "_id":{"$oid":"5ea08fc9c7c1073b80515d7e"},
    "name":"Theory",
    "username":"Kratos",
}

Equality Filters​

  • Filter documents which have name = Kratos
  • Enter the filter in Compass → Collection → filter field
{ name : "Kratos" }

Ranged Filters​

  • Filter documents which have 60 <= likes[] < 65
{ likes : { $gte: 60 , $lt :65} }

Operators​

  • Special keys with $ sign are called as operators
  • Examples: $gte, $and
  • Read more in Query Operators