Database Reference
In-Depth Information
Format domain
Datatype
Datatype
Captured but not enforced either through a reference, which is sim-
ilar to a foreign key, or through embedded documents.
Relationship
Constraint
Candidate
key
(Primary
or
Alternate
Unique index
Unique index
key)
Globally
Unique
Id
Surrogate key
ObjectId
(GUID)
Foreign key
Foreign key
Reference
Secondary key, Inver-
sion entry
Secondary key
Non-unique index
Subtype
Rolldown, Rollup, Identity
Rolldown, Rollup, Identity
E
NTITIES
An entity represents a collection of information about something that the business deems
important and worthy of capture. A noun or noun phrase identifies a specific entity. An
entity fits into one of six categories: who, what, when, where, why, or how. Here is a defin-
ition of each of these entity categories along with examples.
Category
Definition
Examples
Person or organization of interest to the enterprise. That is, “
Who
is
important to the business?” Often a
Who
is associated with a role such
as Customer or Vendor.
Employee, Patient, Player, Sus-
pect, Customer, Vendor, Student,
Passenger, Competitor, Author
Who
