1    db.coll.findOne() // returns a single document
2    db.coll.find()    // returns a cursor - show 20 results - "it" to display more
3    db.coll.find().pretty()
4    db.coll.find({name: "Max", age: 32}) // implicit logical "AND".
5    db.coll.find({date: ISODate("2020-09-25T13:57:17.180Z")})
6    db.coll.find({name: "Max", age: 32}).explain("executionStats") // or "queryPlanner" or "allPlansExecution"
7    db.coll.distinct("name")
8    
9    // Count
10    db.coll.count({age: 32})          // estimation based on collection metadata
11    db.coll.estimatedDocumentCount()  // estimation based on collection metadata
12    db.coll.countDocuments({age: 32}) // alias for an aggregation pipeline - accurate count
13    
14    // Comparison
15    db.coll.find({"year": {$gt: 1970}})
16    db.coll.find({"year": {$gte: 1970}})
17    db.coll.find({"year": {$lt: 1970}})
18    db.coll.find({"year": {$lte: 1970}})
19    db.coll.find({"year": {$ne: 1970}})
20    db.coll.find({"year": {$in: [1958, 1959]}})
21    db.coll.find({"year": {$nin: [1958, 1959]}})
22    
23    // Logical
24    db.coll.find({name:{$not: {$eq: "Max"}}})
25    db.coll.find({$or: [{"year" : 1958}, {"year" : 1959}]})
26    db.coll.find({$nor: [{price: 1.99}, {sale: true}]})
27    db.coll.find({
28      $and: [
29        {$or: [{qty: {$lt :10}}, {qty :{$gt: 50}}]},
30        {$or: [{sale: true}, {price: {$lt: 5 }}]}
31      ]
32    })
33    
34    // Element
35    db.coll.find({name: {$exists: true}})
36    db.coll.find({"zipCode": {$type: 2 }})
37    db.coll.find({"zipCode": {$type: "string"}})
38    
39    // Aggregation Pipeline
40    db.coll.aggregate([
41      {$match: {status: "A"}},
42      {$group: {_id: "$cust_id", total: {$sum: "$amount"}}},
43      {$sort: {total: -1}}
44    ])
45    
46    // Text search with a "text" index
47    db.coll.find({$text: {$search: "cake"}}, {score: {$meta: "textScore"}}).sort({score: {$meta: "textScore"}})
48    
49    // Regex
50    db.coll.find({name: /^Max/})   // regex: starts by letter "M"
51    db.coll.find({name: /^Max$/i}) // regex case insensitive
52    
53    // Array
54    db.coll.find({tags: {$all: ["Realm", "Charts"]}})
55    db.coll.find({field: {$size: 2}}) // impossible to index - prefer storing the size of the array & update it
56    db.coll.find({results: {$elemMatch: {product: "xyz", score: {$gte: 8}}}})
57    
58    // Projections
59    db.coll.find({"x": 1}, {"actors": 1})               // actors + _id
60    db.coll.find({"x": 1}, {"actors": 1, "_id": 0})     // actors
61    db.coll.find({"x": 1}, {"actors": 0, "summary": 0}) // all but "actors" and "summary"
62    
63    // Sort, skip, limit
64    db.coll.find({}).sort({"year": 1, "rating": -1}).skip(10).limit(3)
65    
66    // Read Concern
67    db.coll.find().readConcern("majority")