04 - MongoDB Data Structures

Question 1

Explain in human terms

MONGO_HOST = “172.31.90.91”

Answer 1

replace with your server’s private IP address

Question 2

Explain in human terms

MONGO_DB = "my_db"

Answer 2

name of database in the MongoDB server that you want to use

Question 3

db = client[MONGO_DB]

Answer 3

• If the database with the specified name does not exist, it gets created.
• Note that the database gets created after data is added to it

Question 4

movies = db[“movies”]

Answer 4

• If the collection does not exist yet, this will create a collection named movies
• in the database that is currently being used

Question 5

Explain in human terms
result = movies.insert_one( { “title” : “Jaws” } )

Answer 5

• inserts one document in the movies collection
• will return an InsertOneResult object

Question 6

result.inserted_id

Answer 6

• to get the ObjectID
• the inserted_id property holds the id of the inserted document

Question 7

What happens when you don’t assign an id to a document?

Answer 7

MongoDB will create one automatically

Question 8

Will this work? Why/why not?

movies.insert_one( { "_id" : [ "Star Wars",
                             	"The Empire Strikes Back",
                             	"Return of the Jedi" ] } )

Answer 8

No
_id shouldn’t be an array

Question 9

Will this work? Why/why not?

movies.insert_one( { “Star Wars” } )

Answer 9

no
wrong format

Question 10

Will this work? Why/why not?

movies.insert_one( { "_id" : "Star Wars" } )

Answer 10

Yes
* not an array
* follows format

Question 11

When will this not work?

result = movies.insert_many( [ { "_id" : "Batman", "year" : 1989 },
                    	{ "_id" : "Home Alone", "year" : 1990 },
                    	{ "_id" : "Ghostbusters", "year" : 1984 },
                    	{ "_id" : "Ghostbusters", "year" : 1984 },
                    	{ "_id" : "Lord of the Rings", "year" : 2001} ] )
result.inserted_ids

Answer 11

the second ghostbusters

Question 12

What happens when an insert fails?
Ordered vs Unordered

Answer 12

Ordered
* will stop processing inserts upon encountering an error.

Unordered
* will still attempt all of the others.
* inserts may be executed in a different order than you specified.

Question 13

How to specify an insert is unordered?

Answer 13

ordered = False

Question 14

Define

Field

Answer 14

key-value pair, a MongoDB document can have several fields

Question 15

Differentiate

Field name and key

Answer 15

same

Question 16

List

ways to delete

4

Answer 16

movies.delete_one()
movies.delete_many()
movies.drop() or db.drop_collection("movies")

Question 17

What will be the result?

movies.find({"_id" : ObjectId("5b963e71175f8feddc46f1c3")}, {"title":0})

Answer 17

movie with specified id, no title

Question 18

What will be the result?

movies.find({}, {"title":1})

Answer 18

gets all movies and shows title

Question 19

What will the results of these be?

movies.find()
movies.find({})

Answer 19

both the same, gets all

Question 20

When you use find(), MongoDB returns a pointer to the result set called?

Answer 20

cursor

Question 21

Is cursor.hasNext() used in both mongosh and PyMongo?

Answer 21

mongosh only

Question 22

How to sort

Answer 22

testcol.find().sort("a",1)
1 for ascending, -1 for descending

Question 23

How to sort multiple keys?

Answer 23

testcol.find().sort([("a",1),("b",-1)])

Question 24

Limit result & skip some results

Answer 24

testcol.find().sort("a",1).limit(5).skip(5)

Question 25

# Define $lt

Answer 25

Exists and is less than

Question 26

# Define $lte

Answer 26

Exists and is less than or equal to

Question 27

# Define $gt

Answer 27

Exists and is greater than

Question 28

# Define $gte

Answer 28

Exists and is greater than or equal to

Question 29

# Define $eq

Answer 29

Equal to

Question 30

# Define $ne

Answer 30

Does not exist or does but is not equal to

Question 31

# Define $in

Answer 31

Exists and is in a set

Question 32

$nin

Answer 32

Does not exist or is not in a set

Question 33

Exists and is less than

Answer 33

# Define $lt

Question 34

Exists and is less than or equal to

Answer 34

# Define $lte

Question 35

Exists and is greater than

Answer 35

# Define $gt

Question 36

Exists and is greater than or equal to

Answer 36

# Define $gte

Question 37

Equal to

Answer 37

# Define $eq

Question 38

Does not exist or does but is not equal to

Answer 38

# Define $ne

Question 39

Exists and is in a set

Answer 39

# Define $in

Question 40

Does not exist or is not in a set

Answer 40

$nin

Question 41

# Define $or

Answer 41

Match either of two or more values

Question 42

# Define $not

Answer 42

Used with other operators

Question 43

# Define $nor

Answer 43

Match neither of two or more values

Question 44

# Define $and

Answer 44

Match both of two or more values

Question 45

# List Logical Query Operators | 4

Answer 45

$or $not $nor $and

Question 46

Match either of two or more values

Answer 46

# Define $or

Question 47

Used with other operators

Answer 47

# Define $not

Question 48

Match neither of two or more values

Answer 48

# Define $nor

Question 49

Match both of two or more values

Answer 49

# Define $and

Question 50

# List Comparison Query Operators | 8

Answer 50

$gt $gte $lt $lte $eq $ne $in $nin

Question 51

# Simplify `movies.find({"title" : {"$not" : {"$in" : ["Batman", "Godzilla"]}}})` | Find all movies that are not batman or Godzilla

Answer 51

`movies.find({"title":{"$nin":["Batman","Godzilla"]}})`

Question 52

# Simplify `movies.find({"$nor": [ { "category" : {"$in": [ "action" ]} }, { "category" : {"$in": [ "adventure" ]} }]} )` | Finds neither action nor adventure movies

Answer 52

`movies.find({"$nor":[{"category":{"$in":["action","adventure"]}}]})`

Question 53

Find all sci-fi movies

Answer 53

`movies.find({"category": "sci-fi"})`

Question 54

Find either sci-fi or comedy movies

Answer 54

`movies.find({"category":{"$in":["sci-fi","comedy"]}})`

Question 55

Find all movies that made profit

Answer 55

`movies.find({"$expr": {"$gt": [ "$revenue" , "$budget" ]}})` * compares revenue > budget

Question 56

# List Array Query Operators | 3

Answer 56

* **$all**: Array field must contain all values listed. * **$size**: Array must have a particular size. e.g. $size : 2 means 2 elements in the array * **$elemMatch**: All conditions must be matched by at least one element in the array

Question 57

# Differentiate `db.movies.find( { "category" : { "$all" : [ "sci-fi", "action" ] } } )` And ``` db.movies.find( { "category" : { $in : [ "sci-fi", "action" ] } } ) ```

Answer 57

$all: has both sci-fi and action $in: basta in the set

Question 58

$all

Answer 58

Array field must contain all values listed

Question 58

$size

Answer 58

Array must have a particular size. e.g. $size : 2 means 2 elements in the array

Question 59

$elemMatch

Answer 59

All conditions must be matched by at least one element in the array

Question 60

Array field must contain all values listed

Answer 60

$all

Question 61

Array must have a particular size. e.g. $size : 2 means 2 elements in the array

Answer 61

$size

Question 62

All conditions must be matched by at least one element in the array

Answer 62

$elemMatch

Question 63

# Code All movies with 3 categories

Answer 63

`movies.find( { "category" : { "$size" : 3 } } )`

Question 64

# Code All sci-fi and action movies

Answer 64

`movies.find( { "category" : { "$all" : [ "sci-fi", "action" ] } } )`

Question 65

Find movies that were filmed in Florence, Italy using $elemMatch

Answer 65

``` movies.find( { "filming_locations" : { "$elemMatch" : { "city" : "Florence", "country" : "Italy" } } } ) ```

Question 66

# LIst Update Functions | 3

Answer 66

``` replace_one() update_one() update_many() ```

Question 67

Differentiate ``` replace_one() update_one()```

Answer 67

replace: whole document update: mutates

Question 68

$inc

Answer 68

Increment a field’s value by the specified amount

Question 69

$mul

Answer 69

Multiply a field’s value by the specified amount

Question 70

$rename

Answer 70

Rename a field

Question 71

$min

Answer 71

Updates the field value to a specified value if the specified value is less than the current value of the field

Question 72

$max

Answer 72

Updates the field value to a specified value if the specified value is greater than the current value of the field

Question 73

$currentDate

Answer 73

Set the value of a field to the current date or timestamp.

Question 74

Increment a field’s value by the specified amount

Answer 74

$inc

Question 75

Multiply a field’s value by the specified amount

Answer 75

$mul

Question 76

Rename a field

Answer 76

$rename

Question 77

Updates the field value to a specified value if the specified value is less than the current value of the field

Answer 77

$min

Question 78

Updates the field value to a specified value if the specified value is greater than the current value of the field

Answer 78

$max

Question 79

Set the value of a field to the current date or timestamp.

Answer 79

$currentDate