mongodb

Question 1

how to load up mongo

Answer 1

mongod on command line

Question 2

mondodb - what is the equivalent of an sql table

Answer 2

collection

Question 3

mongodb - delete document where category is sandwich

Answer 3

@col.remove({‘category’ => “sandwich”}) # note how it uses same parameters as in find method

Question 4

mongodb - equivalent of sql column

Answer 4

bson field

Question 5

mongodb - equivalent of sql primary key

Answer 5

_id field

Question 6

mongodb - equivalent of sql row

Answer 6

bson document

Question 7

mongodb - find all emails (a field) with gmail in it

Answer 7

collection.find {:email => /gmail/i }

Question 8

mongodb - get all unique tags in the system

Answer 8

posts.distinct(‘tags’)

Question 9

mongodb - how to decide whether to embed an object or not

Answer 9

look at how you work with objects in your software an entity should get its own collection if you frequently work with that entity by itself.

Question 10

mongodb - what’s wrong with this data structure: {“_id”=>BSON::ObjectId4eeff4dad27d20f1b500011e, “name”=>{“Margaret Nicholson”=>[#data]}}

Answer 10

should be: {“_id”=>BSON::ObjectId4eeff4dad27d20f1b500011e, “name”=>”Margaret Nicholson” “data”=>[]} why? easier access with queries (db.facebook_likes.find{name:/Margaret/})

Question 11

mongodb - why don’t you need a created_at column

Answer 11

since the _id includes a timestamp thus this is chronological order posts.find.sort( [[‘_id’, -1]] )

Question 12

mongodb posts.find( :tags => ‘mongo’ ) add an index to make this more efficient

Answer 12

posts.create_index(‘tags’)