MongoDB - Dynamic_Schema/MongoImport/Cursor/Queries/Sorting

Dynamic Schema
-Polymorphism

Schemaless / Polymorphism

--add new fields easily to schema

Things

{Shape:"Rect",x:3,y:4,Area:12}

{Shape:"Circle",radius:1,Area:3.14}

Mongo Import

Open another command prompt

mongoimport.exe can import 3 types of files CSV,TSV,JSON

mongoimport --db databasename --collection tablename < filename

mongoimport --stopOnError

mongoimport --db pcat --collection products < products.json

Mongo Shell Queries

--show recordcount

db.collection.count()

--show all rows

db.collection.find()

--Show only name column

db.collection.find({},{name:1})

--show all rows nicely

db.collection.find().toArray()

--show only 10 rows nicely 

db.collection.find({}).limit(10).toArray()

--Show only 1 row

db.collection.findOne()

db.collection.find({}).limit(1)

--Skip first 2 and give next 4

db.collection.find({}).limit(4).Skip(2)   -

--Turn off Id

db.collection.find({},{name:1,_id:0})

--Get Name and Brand

db.collection.find({},{name:1,brand:1})

--All fields and 1 row

db.collection.find({}).limit(1)

--if the output is not too big

db.collection.find({}).limit(3).toArray()

--query price = 12.5

db.collection.find({price:12.5})

db.collection.find({price:12.5}).toArray()

db.collection.find({},{price:1})

--Object id is bson type, not string

-- Get one document

db.collection.findOne({"_id": ObjectId("ddadfa5464565fgafaddadffadfadfgffd")})

db.collection.find({price:200},{name:1,price:1})

--greater than

db.collection.find({price: {$gte:200}},{name:1,price:1})

$Operators

Querying

$gte

$gt

$lt

$lte

$or

$not

$nin

$in

$type

$exists

Updating

$inc

$set

$addToSet

--greater than and expression

db.collection.find({price: {$gte:200},available:true},{name:1,price:1,available:1})

--find ac3 is in array

db.collection.find({for : "ac3"}) 

Reaching into Nested Documents

dot notation

find({"x.a":1})

Quiz

Add caption

db.collection.find({for:"ac9",Type:"case"}).toArray()

Sorting

db.collection.find(_).sort(fieldname:direction)

db.collection.find({},{name:1,price:1}).sort({price:1})

-- null is less than number

--sort rows only with price

db.collection.find({price:{$exists:true}},{name:1,price:1}).sort({price:1})

db.collection.find({price:{$exists:true}},{name:1,price:1}).sort({price:-1})

Multiple Sort keys

db.collection.find().sort({lastname:1,firstname:1})

--SQL order by lastname,firstname

Cursors (different from other database)

db.test.find()

type it for more

db.test.find().skip(20).limit(5)

--skip is expensive, 20 is fine if 5000 is expensive.

--sort and skip is done at the server

Example

var cursor = db.test.find()

cursor.hasNext()