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Normalization in DB2 – first normal form, second normal form
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Answer / mohan.s
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.
| Is This Answer Correct ? | 7 Yes | 1 No |
Answer / mohan.s
First 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.
| Is This Answer Correct ? | 7 Yes | 3 No |
Answer / mohan.s
The formal classifications describing the level of database
normalization in a data model are called Normal Forms (NF)
and the process of doing this is Normalization.
| Is This Answer Correct ? | 8 Yes | 6 No |
Answer / mohan.s
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.
| Is This Answer Correct ? | 4 Yes | 3 No |
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