Mongo DB

Question 1

What is the MongoDB syntax to write a JSON range query?

Answer 1

{fieldname:{$gte: numx, $lt: numy}}

Question 2

What is the syntax to create a database?

Answer 2

use

Question 3

What is the MongoDB syntax to find a collection within the command line?

Answer 3

db.collection_name.find()

Question 4

what is the Mongo CLI syntax to insert multiple documents?

Answer 4

db.post.insertMany([])

Question 5

How do you specify, or access field in an embedded document?

Answer 5

”..“

To specify or access a field of an embedded document with dot notation, concatenate the embedded document name with the dot (.) and the field name, and enclose in quotes:

db.post.find({‘username.fname’:’John’})

Question 6

What is the syntax to find an array length?

Answer 6

db..find( { “tags”: { $size: 3 } } )

Question 7

What is the syntax for AND in a ‘find’ clause?

Answer 7

db..find({$and:[{“Username”:”Alex”},{“title”:”NoSQL Database”}]}).pretty()

Question 8

How do you use find with a specific clause

Answer 8

db.post.find( {:]} )

example
db.post.find( {tags:[ ‘mongodb’, ‘database’, ‘NoSQL’]} )

Question 9

What is the MongoDB command line syntax to query an array by array length

Answer 9

db.find({:})

example
db.post.find( { “tags”: {$size:3}})

Question 10

What is the mongoDB command line syntax to update a document?

Answer 10

db.mycol.update({:},{$set:{:}})

Question 11

What is the MongoDB command line syntax to insert multiple documents into a collections

Answer 11

db. .insertMany([{:,,,:},{BSONFILE2},{BSONFILE3}])

* FYI:: ‘insertMany’ takes in an array.

Question 12

What is the MongoDB command line syntax to delete a collection

Answer 12

db..drop()

Question 13

What is the MongoDB command line syntax to rename a collection

Answer 13

db..renameCollection()

Question 14

What is the MongoDB CLI syntax to iterate through a field to see if it equates to a boolean statement?

Answer 14

db.records.aggregate( [
{ $project: { : { $eq: [ “”, { $literal:} ] } } }
] )

Question 15

What formats does MongoDB accept?

Answer 15

Use Json and Bson for documents.

Question 16

What is the normalized data model? and when should you use it?

Answer 16

Normalized data models describe relationships using references between documents.

Question 17

In general, when should you use normalized data models?

Answer 17

➢ when embedding would result in duplication of data but would not provide sufficient read performance advantages to outweigh the implications of the duplication.
➢ to represent more complex many-to-many relationships
➢ to model large hierarchical data sets.

Question 18

Per the MongoDB University course, what argument can we pass through so that mongo DB continues inserting even if it contacts an error

Answer 18

{
‘ordered’: false
}

Question 19

in MongoDB, what syntax goes after a projection query to get rid of the primary key (or any other field in a projection for that matter)

Answer 19

Setting a file to ‘:0’ in the projection field

I.E. _id:0

db.COLLECTIONNAME.find({FILTER(S)}, {PROJECTION, _id:0}

E.G: db.movies.find({genre:’drama’},{title, _id=0}

Question 20

In MongoDB, what syntax goes within projection parameter of query to explicitly return respective field, and exclude all others

Answer 20

set a respective field to ‘1’

E.G.: db.movies.find({genre:’drama’},{title:1}

Question 21

What method call is used to remove a specific field

Answer 21

$unset

Question 22

What does upsert stand for in MongoDB. In which line does it appear in a Mongo query?

Answer 22

if exists update, if not then insert. it appears as the third parameter in an update

Question 23

what does the $all operator do?

Answer 23

helps you find a combination of values for a given array within a query

e. g.
db. movies.find({genres:{$all: ‘Romance’, ‘comedy’,’action’}},{title:0})

Question 24

what function can you use to get a count of a query

Answer 24

.count()

e. g.
find. movies.find({countries:{$size:1}}).count()

Question 25

what are the three popular array operators shown in MongoDB?

Answer 25

1) $all: – takes in an array []
2) $size: (is enclosed within {})
3) $elemMatch: (enclosed within {} )

bonus:
4) $in: [ ] ## takes in an array
5) $nin [ ]

Question 26

When are $and and $or used during a MongoDB?

Answer 26

When the query has two parameters for the same field. Otherwise, a query is only ran with the second search parameter for the given field.

db.post.find({$and:[arg1, arg2]})

Question 27

What coding language does the MongoDB shell interpret in?

Answer 27

The Mongo shell is a JavaScript.

Question 28

how is $in used in MongoDB queries?

Answer 28

db.inventory.find( { qty: { $in: [ 5, 15 ] } } )

Question 29

What is the syntax in Mongo for $elematch queries? what can you not specify

Answer 29

{ : { $elemMatch: { query1, query2, … } } }

You cannot specify a $where expression in an $elemMatch.
You cannot specify a $text query expression in an $elemMatch.