<s>
In	O
database	B-Application
normalization	I-Application
,	O
unnormalized	B-Application
form	I-Application
(	O
UNF	O
)	O
,	O
also	O
known	O
as	O
an	O
unnormalized	O
relation	O
or	O
non-first	O
normal	B-Application
form	I-Application
(	O
N1NF	O
or	O
NF2	O
)	O
,	O
is	O
a	O
database	O
data	B-Application
model	I-Application
(	O
organization	O
of	O
data	O
in	O
a	O
database	O
)	O
which	O
does	O
not	O
meet	O
any	O
of	O
the	O
conditions	O
of	O
database	B-Application
normalization	I-Application
defined	O
by	O
the	O
relational	B-Architecture
model	I-Architecture
.	O
</s>
<s>
Database	O
systems	O
which	O
support	O
unnormalized	O
data	O
are	O
sometimes	O
called	O
non-relational	O
or	O
NoSQL	B-General_Concept
databases	O
.	O
</s>
<s>
In	O
the	O
relational	B-Architecture
model	I-Architecture
,	O
unnormalized	O
relations	B-Language
can	O
be	O
considered	O
the	O
starting	O
point	O
for	O
a	O
process	O
of	O
normalization	B-Application
.	O
</s>
<s>
It	O
should	O
not	O
be	O
confused	O
with	O
denormalization	O
,	O
where	O
normalization	B-Application
is	O
deliberately	O
compromised	O
for	O
selected	O
tables	O
in	O
a	O
relational	O
database	O
.	O
</s>
<s>
In	O
1970	O
,	O
E	O
.	O
F	O
.	O
Codd	O
proposed	O
the	O
relational	B-Architecture
data	I-Architecture
model	I-Architecture
,	O
now	O
widely	O
accepted	O
as	O
the	O
standard	O
data	B-Application
model	I-Application
.	O
</s>
<s>
At	O
that	O
time	O
,	O
office	B-Application
automation	I-Application
was	O
the	O
major	O
use	O
of	O
data	O
storage	O
systems	O
,	O
which	O
resulted	O
in	O
the	O
proposal	O
of	O
many	O
NF2	O
data	B-Application
models	I-Application
like	O
the	O
Schek	O
model	O
,	O
Jaeschke	O
models	O
(	O
non-recursive	O
and	O
recursive	O
algebra	O
)	O
,	O
and	O
the	O
Nested	O
Table	O
Data	O
(	O
NTD	O
)	O
model	O
.	O
</s>
<s>
Moreover	O
,	O
a	O
lot	O
of	O
research	O
has	O
been	O
done	O
and	O
journals	O
have	O
been	O
published	O
to	O
address	O
the	O
shortcomings	O
of	O
the	O
relational	B-Architecture
model	I-Architecture
.	O
</s>
<s>
Since	O
the	O
turn	O
of	O
the	O
century	O
,	O
NoSQL	B-General_Concept
databases	O
have	O
become	O
popular	O
owing	O
to	O
the	O
demands	O
of	O
Web	O
2.0	O
.	O
</s>
<s>
Normalization	B-Application
to	O
first	O
normal	B-Application
form	I-Application
requires	O
the	O
initial	O
data	O
to	O
be	O
viewed	O
as	O
relations	B-Language
.	O
</s>
<s>
In	O
database	O
systems	O
relations	B-Language
are	O
represented	O
as	O
tables	O
.	O
</s>
<s>
In	O
practice	O
,	O
this	O
is	O
ensured	O
by	O
defining	O
one	O
or	O
more	O
columns	O
as	O
primary	B-Application
keys	I-Application
.	O
</s>
<s>
This	O
definition	O
does	O
not	O
preclude	O
columns	O
having	O
sets	O
or	O
relations	B-Language
as	O
values	O
,	O
e.g.	O
</s>
<s>
This	O
is	O
the	O
major	O
difference	O
to	O
first	O
normal	B-Application
form	I-Application
.	O
</s>
<s>
NoSQL	B-General_Concept
databases	O
like	O
Document	B-General_Concept
databases	I-General_Concept
typically	O
does	O
not	O
conform	O
to	O
the	O
relational	O
view	O
.	O
</s>
<s>
But	O
there	O
are	O
also	O
database	O
models	O
which	O
support	O
the	O
relational	O
view	O
,	O
but	O
does	O
not	O
embrace	O
first	O
normal	B-Application
form	I-Application
.	O
</s>
<s>
Such	O
models	O
are	O
called	O
non-first	O
normal	B-Application
form	I-Application
relations	B-Language
(	O
abbreviated	O
NFR	O
,	O
N1NF	O
or	O
NF2	O
)	O
.	O
</s>
<s>
This	O
is	O
a	O
valid	O
relation	O
but	O
does	O
not	O
conform	O
to	O
first	O
normal	B-Application
form	I-Application
which	O
does	O
not	O
allow	O
nested	O
relations	B-Language
.	O
</s>
<s>
Today	O
,	O
companies	O
like	O
Google	B-Application
,	O
Amazon	B-Application
and	O
Facebook	B-Application
deal	O
with	O
large	O
amounts	O
of	O
data	O
that	O
are	O
difficult	O
to	O
store	O
efficiently	O
.	O
</s>
<s>
They	O
use	O
NoSQL	B-General_Concept
databases	O
,	O
which	O
are	O
based	O
on	O
the	O
principles	O
of	O
the	O
unnormalized	O
relational	B-Architecture
model	I-Architecture
,	O
to	O
deal	O
with	O
the	O
storage	O
issue	O
.	O
</s>
<s>
Some	O
examples	O
of	O
NoSQL	B-General_Concept
databases	O
are	O
MongoDB	B-Application
,	O
Apache	B-Application
Cassandra	I-Application
and	O
Redis	B-Operating_System
.	O
</s>
<s>
These	O
databases	O
are	O
more	O
scalable	B-Architecture
and	O
easier	O
to	O
query	B-Language
with	O
as	O
they	O
do	O
not	O
involve	O
expensive	O
operations	O
like	O
JOIN	B-Language
.	O
</s>
