Answer Posted / nivedita
Normalization is the process of designing a datamodel and
effociently store the data in a databaseFirst normal form
(1NF) lays the groundwork for an organised database design:
Ensure that each table has a primary key: minimal set of
attributes which can uniquely identify a record.
Eliminate repeating groups (categories of data which would
seem to be required a different number of times on
different records) by defining keyed and non-keyed
attributes appropriately.
Atomicity: Each attribute must contain a single value, not
a set of values.
'First normal form' depends on functional dependency
formula f(x)=y. For every value of x there is value for y.
Second normal form
Second normal form (2NF) If a table has a composite key,
all attributes must be related to the whole key:
The database must meet all the requirements of the first
normal form.
The relational schema should not have any partial
functional dependency i.e. No proper subset of the primary
key should derive a functional dependency belonging to the
same schema. For example, consider functional dependencies
FD:{AB->C, A->D, C->D} here AB is the primary key, as A->D
this relational schema is not in 2NF.
Third normal form
Third normal form (3NF) requires that data stored in a
table be dependent only on the primary key, and not on any
other field in the table.
The database must meet all the requirements of the first
and second normal form.
All fields must be directly dependent on the primary key
field. Any field which is dependent on a non-key field
which is in turn dependent on the Primary Key (ie a
transitive dependency) is moved out to a separate database
table.
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