As part of our MongoDB Guide, we’ve compiled this cheat sheet of common and not-so-common MongoDB commands.
Table of Contents
Pretty Print
Create Collection
Create Indexes
Create index
Create sparse index
Create compound index
Create geo index
Create partial index
Add and Delete Data
Add one data record
Add array (many) records
Delete data
Query MongoDB Documents
Search by attribute
Search by geolocation
Search greater or less than
Search not equal to
Search and return only certain fields
Search by regular expression
Find by elements in array
Replication and Sharding
Enable replication
Add shard
Show Server Memory
Aggregate functions
MapReduce
Pretty Print
Add pretty() to the end of any search:
db.collection.find({}).pretty()
Create Collection
db.createCollection("<collection name>")
Create Indexes
Create index
The format is {attribute : sortOrder} where sort order is -1 (descending) or 1 (ascending).
db.cars.createIndex( { make: 1 } )
Create sparse index
This does not index documents that do not have this attribute.
db.products.createIndex({product:-1},{sparse: true})
Create compound index
db.cars.createIndex( { make: 1 , model: -1} )
Create geo index
db.address.createIndex( { "location": "2dsphere"} )
Create partial index
This indexes those documents that match the search criteria.
db.students.createIndex(
{ age: 1},
{ partialFilterExpression: { age: { $gt: 14}}}
)
Add and Delete Data
Add one data record
db.cars.insert([
{
vin: 1111111111,
model: 'SK-202',
make: 'Mercedes'
}
])
Add array (many) records
db.cars.insertMany([
{
vin: 1111111111,
model: 'SK-202',
make: 'Mercedes'
},
{
vin: 2222222,
model: 'Cabriolet',
make: 'Chevrolet' }
])
Delete data
db.cars.remove({"make": "Chevrolet"})
Query MongoDB Documents
Search by attribute
db.cars.find({ "make": "Mercedes"}
Search by geolocation
db.address.find ({
location: {
$near: {
$geometry: {
type: "Point" ,
coordinates: [ -72.7738706,41.6332836 ]
},
$maxDistance: 4,
$minDistance: 0
}
}
})
Search greater or less than
db.sales.find({"price": {$gt: 100}})
Search not equal to
db.cars.find({make: {$not: {$eq: "Mercedes"}}})
Search and return only certain fields
This is called projection.
Show only the make field:
db.cars.find({make: "Mercedes"}, {vin: -1})
Show every field except the make field:
db.cars.find({make: "Mercedes"}, {vin: 0})
Search by regular expression
You can use the slash or quote marks as a delimiter.
db.cars.find({"make": {$regex: /^M.*/}})
Case insensitive:
db.cars.find({"make": {$regex: /^merc.*/, $options: "i"}} )
Find by elements in array
This matches documents that contain all of these array elements:
db.manufacturers.find({"name": {$all: [ "Mercedes", "Ford" ]}} )
Match on any element in the array:
db.manufacturers.find({"name": "Ford"} )
Replication and Sharding
Enable replication
Connect to a config server then:
rs.initiate()
And then show replication status:
rs.status()
Add shard
Connect to query router (mongos) server. 27018 in this example is the port number of a shard server
sh.addShard( "ShardReplSet/172.31.47.43:27018")
Show Server Memory
db.serverStatus().mem
Aggregate functions
This is the same as the SQL select count(*) from words group by word. This is the word count program.
db.words.aggregate([ {$group: { _id: "$word", cnt: {$sum: 1} } } ])
MapReduce
You can do the same word count function using the map operation:
db.words.mapReduce(
function() { emit(this.word,1); },
function(key, values) {return Array.sum(values)}, {
query:{},
} out:"total_matches"
).find()
