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find()​

  • find() function is used to fetch documents
db.collection_name.find()
  • Without any arguments, find() fetches all documents in the collection

Single Selector​

  • Use find(equality_filter) to find documents
db.games.find({ platform: "PS4" })
  • Returns documents with platform type PS4
note

NOTE: Use pretty() to view results in json format. Example: db.collection_name.find(equality_filter).pretty()

Multiple selectors​

db.games.find({ platform: "PS4", year: 2018 })
  • Returns documents with platform type PS4 and released in year 2009
note

NOTE: By default multiple selectors are filtered by AND logic

Embedded/Nested documents​

{
    title: "God of War",
    platform: "PS4",
    ratings: {
        ign: 10,
        gamespot: 9.8,
        metacritic: 99,
    }
}
  • Use dot-notation to filter with embedded/nested document fields
db.games.find({ "ratings.ign": 10 })
  • Returns documents which were rated 10 by ign
note

NOTE: Nesting can be done for multiple levels. { wind.direction.angle: 290 }

note

NOTE: When running nested filters in shell key should be enclosed in quotes { "wind.direction.angle": 290 }

note

TIP: Use .count() to find number of filter documents. Example: db.collection_name.find(equality_filter).count()

Array Fields​

{
    title: "The Last of Us",
    platform: "PS4",
    cast: ["Troy Baker", "Ashley Johnson", "Nolan North" ]
}

Exact match​

  • Pass array in selector to find the documents which have EXACT match in elements AND their order
db.games.find({ cast: ["Troy Baker", "Ashley Johnson"] })
  • Returns documents which have cast = ["Troy Baker", "Ashley Johnson"]

Filter for single element​

  • Find value in selector to find documents which have the passed filter in the array
db.games.find({ cast: "Troy Baker" })
  • Returns documents which have the "Troy Baker" as one of the cast members. There may be other members as well in the array

Filter along with position/index​

db.games.find({ "cast.0": "Troy Baker" })
  • Returns documents in which "Troy Baker" is the FIRST element in cast array

Cursors​

  • By default mongodb shell returns a cursor for a query which contains 20 documents
  • To view the next documents in:
    • Compass: Click next button for next 20 documents
    • Shell: Type it to iterate through next 20 documents

Projections​

Projections are objects passed as second argument to the find() function to LIMIT the fields in the fetched documents

Include only specific fields​

db.games.find({ platform: "PS4" }, { title: 1 })
  • Returns ONLY _id & title fields in the resultant documents
Output
{
    "_id" : ObjectId("5ee3ac9e8596ceb79d3fd7f9"),
    "title" : "God of War",
}
{
    "_id" : ObjectId("5ee3ac9e8596ceb79d3fd7fc"),
    "title" : "The Last of Us",
}

Exclude only specific fields​

db.games.find({ platform: "PS4" }, { _id: 0, cast: 0 })
  • Returns ALL BUT _id & cast fields in the resultant documents
Output
{
    "title" : "God of War",
    platform: "PS4",
}
{
    "title" : "The Last of Us",
    platform: "PS4",
}

Combine​

db.games.find({ platform: "PS4" }, { title: 1, _id: 0 })
  • Returns ONLY title field in the resultant documents
Output
{
    "title" : "God of War"
}
{
    "title" : "The Last of Us"
}