Andrew Dorokhov
Database operations
db.version() // Server version
db.help() // List of commands
db.stats() // Stats
List and select databases:
show dbs // List databases
use <database> // Switch to a database (creates it on first write)
Collections
db.createCollection('posts') // Create collection
show collections // List collections
Document count:
db.<collectionName>.count({ /* query */ })
Insert documents
db.<collectionName>.insertOne({ /* ... */ })
db.<collectionName>.insertMany([{ /* ... */ }, { /* ... */ }])
Find documents
db.<collectionName>.find({ /* query */ })
db.<collectionName>.findOne({ /* query */ })
db.<collectionName>.find({}) // All documents
db.<collectionName>.findOne({}) // First document
Helpers
Chain these after find():
sort()limit()skip()
Examples:
.find({}).limit(5)
.find({}).skip(2) // Skip the first two
.find({}).sort({ comments: 1 }) // ASC
.find({}).sort({ comments: -1 }) // DESC
Default sort order is by _id ascending.
Query operators
$or,$and$in,$nin$eq,$ne$lt,$gt$regex
Examples:
db.getCollection('posts').find({ comments: { $gt: 0 } })
db.getCollection('posts').find({
$and: [
{ comments: { $lt: 5 } },
{ comments: { $gt: 0 } }
]
})
db.getCollection('posts').find({
tags: {
$in: ['programming', 'coding']
}
})
Update documents
db.<collectionName>.updateOne(<query>, <update>, <options>)
db.<collectionName>.updateMany(<query>, <update>, <options>)
Update operators (second argument):
$set$rename$unset$currentDate$inc— increment$addToSet
$set
db.posts.updateOne(
{ postId: 2452 },
{ $set: { shared: true } }
);
$unset
Removes fields. Example — remove quantity and instock from the first product where sku is "unknown":
db.products.updateOne(
{ sku: 'unknown' },
{ $unset: { quantity: '', instock: '' } }
)
$inc
Increments a numeric field (here by 1):
db.posts.updateOne(
{ postId: 4352 },
{ $inc: { comments: 1 } }
);
Delete documents
db.<collectionName>.deleteOne({ /* query */ })
db.<collectionName>.deleteMany({ /* query */ })
Examples:
db.getCollection('posts').deleteOne({ postId: NumberInt(1111) })
db.getCollection('posts').deleteMany({ title: { $exists: false } })