This document discusses schema design in MongoDB. It begins with an agenda covering core concepts, modeling data, and modeling relationships. It then discusses how MongoDB documents allow for flexible, optimal schemas compared to relational databases. Examples are provided for embedding and referencing data in one-to-one, one-to-many, and many-to-many relationships. The document recommends modeling embedded data when performance is important and referencing data otherwise. Finally, resources for learning more about MongoDB are provided.

1. Schema Design
Bob Grabar
Technical Writer, MongoDB, Inc.
bob@mongodb.com

2. Agenda
• Core Concepts
• Modeling Data
• Modeling Relationships

3. Schema design is about
your Application

4. Relational  Normalize

5. {
MongoDB
"patient_id": "1177099",
"first_name": "John",
"last_name": "Doe",
"dob": "2000-01-25",
"gender": "Male",
"blood_type": "B+",
"address": "123 Elm St., Chicago, IL 59923",
"height": "66",
"weight": "110",
"allergies": ["Nuts", "Penicillin", "Pet Dander"],
"current_medications": [{"name": "Zoloft",
"dosage": "2mg",
"frequency": "daily",
"route": "orally"}],
"complaint" : [{"entered": "2000-11-03",
"onset": "2000-11-03",
"prob_desc": "",
"icd" : 250.00,
"status" : "Active"},
{"entered": "2000-02-04",
"onset": "2000-02-04",
"prob_desc": "in spite of regular exercise...",
"icd" : 401.9,
"status" : "Active"}],
"diagnosis" : [{"visit" : "2005-07-22" ,
"narrative" : "Fractured femur",
"icd" : "9999",
"priority" : "Primary"},
{"visit" : "2005-07-22" ,
"narrative" : "Type II Diabetes",
"icd" : "250.00",
"priority" : "Secondary"}]
}

6. Terminology
RDBMS
MongoDB
Table
Collection
Row
Document
Index
Index
Join
Embedded Document
Foreign Key
Reference

7. Relational Record
• Two-dimensional storage
• Field can contain single value
• Structured schema
• Poor data locality
primary
key

8. MongoDB Document
• Multi-dimensional storage
• Field can contain many values
• Flexible schema
• Optimal data locality
_id

10. Focus on data storage
Focus on data use

11. What answers do I have?
What questions do I have?

12. Modeling Data

13. Business Card

14. Contact
Addres
s

15. Referencing
Contacts
Addresses
{
{
_id : ,
name :
title :
company :
phone :
address_id :
}
_id : ,
street :
city :
state :
",
zip_code :
country :
,
,
",
,
}
,
,
,

16. Embedding
Contacts
{
_id : ,
name :
title :
company :
phone :
address : {
street :
city :
state :
,
zip_code :
country :
}
}
,
,
",
,
,
,
,

17. Schema Flexibility
Contacts
{
name :
url :
title :
,
company :
email :
address : {
street :
city :
state :
,
zip_code :
}
phone :
fax
{
name :
title :
company :
phone :
address : {
street :
city :
state :
,
zip_code :
}
,
,
,
,
,
}
}
,
,
,
,
,
,
,

18. Schema Flexibility
{
{
_id : ,
name :
title :
company :
address : {
street :
city :
state :
,
zip_code :
country :
},
phone :
_id : ,
,
name :
title :
company :
address : [
{
street :
city :
state :
,
zip_code :
country :
},
{
street :
city :
state :
zip_code :
country :
}
],
phone :
,
,
,
,
,
}
}
,
,
,
,
,
,
,
,

19. Modeling Relationships

20. Address Book Entity-Relationship
•
•
•
•
name
location
web
bio
• name
N
1
N
1
1
Contacts
Thumbnails
• mime_type
• data
1
•
•
•
N •
•
type
street
city
state
zip_code
Phones
• name
1 • company
• title
1
1
1
Portraits
• mime_type
• data
Addresses
Groups
Twitters
1
N • type
• number
Emails
N • type
• address

21. One-to-One
•
•
•
•
name
location
web
bio
• name
N
1
N
1
1
Contacts
Thumbnails
• mime_type
• data
1
•
•
•
N •
•
type
street
city
state
zip_code
Phones
• name
1 • company
• title
1
1
1
Portraits
• mime_type
• data
Addresses
Groups
Twitters
1
N • type
• number
Emails
N • type
• address

22. One-to-One
Schema Design Choices
contact
• twitter_id
1
1
twitter
Contact
• twitter
twitter
1

23. One-to-One
General Recommendation
{
_id : ObjectId("52ebde4e5f2b124a3a09eb8e"),
name : "Giovanni Boccaccio",
twitter : {
name : "Gian",
location : "Certaldo",
web : "https://twitter.com/RealBoccaccio"
}
Contact
• twitter
twitter
1
}
db.contacts.find( { "twitter.location" : "Certaldo" } )

24. One-to-Many
•
•
•
•
name
location
web
bio
• name
N
1
N
1
1
Contacts
Thumbnails
• mime_type
• data
1
•
•
•
N •
•
type
street
city
state
zip_code
Phones
• name
1 • company
• title
1
1
1
Portraits
• mime_type
• data
Addresses
Groups
Twitters
1
N • type
• number
Emails
N • type
• address

25. One-to-Many
Schema Design Choices
contact
• phone_ids: [ ]
1
N
phone
Contact
• phones
phone N

26. One-to-Many
Contact Book Application
{
_id : ObjectId("52ebde4e5f2b124a3a09eb8e"),
name : "Giovanni Boccaccio",
twitter : {
name : "Gian",
location : "Certaldo",
web : "https://twitter.com/RealBoccaccio"
},
phones : [
{ type : "work" , number : "+39 0571-669811" },
{ type : "home" , number : "+39 671-946726" },
{ type : "mobile" , number : "+39 671-038747" }
]
}
Contact
• phones
phone N

27. Many-to-Many
•
•
•
•
name
location
web
bio
• name
N
1
N
1
1
Contacts
Thumbnails
• mime_type
• data
1
•
•
•
N •
•
type
street
city
state
zip_code
Phones
• name
1 • company
• title
1
1
1
Portraits
• mime_type
• data
Addresses
Groups
Twitters
1
N • type
• number
Emails
N • type
• address

28. Many-to-Many
Traditional Relational Association
Join Table
Groups
• name
X
GroupContacts
• group_id
• contact_id
Contacts
•
•
•
•
Use arrays instead
name
company
title
phone

29. Many-to-Many
Schema Design Choices
Reference
Embed
group
•
contact_ids: [ ] N N
contact
group
• contacts
contact
group
contact
N N • group_ids: [
]
contact
• groups
N
group
N

30. Many-to-Many
General Recommendation
group
contact
N N • group_ids: [
]
Contact references
groups

31. Many-to-Many
Group embeds contacts
for performance
group
• contacts
contact
N

32. Document model - holistic and efficient representation
Groups
Contacts
• name
N
• name
• company
• title
twitter
N
1
1
Portraits
• mime_type
• data
•
•
•
•
addresses N
1
name
location
web
bio
thumbnail 1
• mime_type
• data
•
•
•
•
•
type
street
city
state
zip_code
phones
N
• type
• number
emails
• type
• address
N

33. Contact document example
{
“name” : “Gary J. Murakami, Ph.D.”,
“company” : “MongoDB, Inc.”,
“title” : “Lead Engineer”,
“twitter” : {
“name” : “Gary Murakami”, “location” : “New Providence, NJ”,
“web” : “http://www.nobell.org”
},
“portrait_id” : 1,
“addresses” :
,
“phones” :
,
“emails” :
}

34. Resources

35. mongodb.org/downloads

37. mongodb.com

38. Thank You
Bob Grabar
Technical Writer, MongoDB, Inc.
bob@mongodb.com