Entity Attribute Value Model
EAV (Entity-Attribute Value) Model
It is a
data model to describe entities where number of attributes for the entities
could be very large in amount.
EAV
helps us to overcome the limitations of conventional database model.
Ex: Organization
‘ABC’ defines the entity ‘Address’ as:
Organization
‘ABC’: Address
|
||||
Line1
|
Line2
|
State
|
Country
|
Zip
|
Organization
‘XYZ’: Address
|
|||||||
Line1
|
Line2
|
Line3
|
City
|
State
|
Country
|
Zip
|
Phone
|
A
conventional database table design (one fact per column or set of facts per
row) is unsuitable for such type of data, because of:
·
the
need to continually add new tables or columns whenever new facts need
incorporation
·
database
vendor limitations on the number of columns per table
Therefore
to deal with the dynamic nature of the data we make use of EAV model.
The
Dynamic Data refers to the data whose structure doesn’t remains constant and
keeps changing from organization to organization.
Understanding EAV model
In
this one each row stores the single fact about an entity. Whereas, in
conventional model a row consist of each column per attribute and each column
consist of a fact which means a set of facts in a row.
Model
comprises of two main parts:
EAV metadata
It
stores data about data. The structure of any data entity is stored in metadata.
The metadata changes as a modification is made in the data entity.
EAV data
It
is the data in the entities. It makes use of the metadata to relate
different attributes of an entity. An EAV table constitutes of an entity, the
attribute and the associated value of that attribute. Conceptually it’s a table
with three columns.
Benefits of EAV
representation:
·
Flexibility:
No limits on number of attributes per entity. Hence, make the table or entity
generic.
·
Space-efficient:
Need not reserve space for attributes whose values are null.
Modeling dynamic data
using EAV model
Ex:
Ex:
EAV metadata tables
Entity types tables:
Entity_id
|
Name
of Entity
|
Description
|
Label
|
TreeDepth
|
101
|
Investigator
|
Profile
of Investigator
|
Null
|
0
|
102
|
Profile
|
Profile
|
Null
|
1
|
105
|
Profile
Details
|
Profile
Details
|
Null
|
2
|
Entity_Type_id
|
Name
of Entity
|
Description
|
Label
|
TreeDepth
|
1
|
String
|
String
Entity
|
Null
|
|
2
|
Date
|
Date
Entity
|
Null
|
|
3
|
Number
|
Number
Entity
|
Null
|
|
4
|
Boolean
|
Boolean
Entity
|
Null
|
|
5
|
List
of Values
|
Select
Single value from a List
|
Null
|
|
6
|
Multi-Select
|
Select
Multiple Value from a list
|
Null
|
Attribute table:
Attribute_id
|
Name
of Attribute
|
Parent_id
|
Entity_Type_id
|
4
|
First
Name
|
102
|
1
|
5
|
Prefix
|
102
|
5
|
EAV Data Tables (String_attribute)
Entity_id
|
Attribute_id
|
Value
|
102
|
4
|
Rishoo
|
102
|
5
|
Er.
|
Other Related Links:
EAV(Entity-Attribute Value) Model
EAV versus Row modeling
Downsides of EAV data model over class row model
Opting classic row modeling or EAV data modeling?
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