what is Normalization ?

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G

Guest

may i know about Normalization and what are
1) first normal form
2) second normal form
3) third normal form
 
If this is a homework question you can always use a search engine to find
some answers. Though I will give you a start:

1) "data integrity"
2) simplifies data entry
 
dear it's not a home work
but i need to know what really they are and how important they are in the
database designing
thanks
 
hi Naveed,

Naveed said:
dear it's not a home work
but i need to know what really they are and how important they are in the
database designing
Click to expand...
Take look at

http://en.wikipedia.org/wiki/Database_normalization

In short: Relational databases utilize some kind of algebra. The
normalization rules are derived from that algebra. Therefore they have
an hugh impact for performance (depending on the RDBMS) and integrity
(independend of any RDBMS).


mfG
--> stefan <--
 
Right out of the text book from Database MAnagement class
Normal Forms
1.First Normal Form (1NF)
A.Eliminate the repeating groups
i.Place in tabular format (make sure each cell has one value)
ii.To eliminate repeating groups, eliminate nulls making sure that each
repeating group attribute contains an appropriate value
B.Identify the Primary key (that identifies each row of data given)
i.Single primary key
ii.Composite keys
C.Identify all dependencies (attributes that depend on the primary key)
i.Partial dependencies – based on only a part of a composite primary key
ii.Transitive dependencies – no attribute is part of any key
D.If you are in 1NF and you have no composite keys, then you are in 2 NF
already
2.Second Normal Formal (2NF)
A.Identify key components and write each component on a separate line, each
becomes a key in a new table
i.All primary keys
ii.All composite keys
B.Assign corresponding dependent attributes
i.Table1(Primary key, all other attributes)
ii.Table 2 (Primary key, all other attributes)
iii.Table 3 (Primary key, all other attributes)
iv.Table 4(Primary key Foreign Key, Primary key Foreign Key , all other
attributes)
3.Third Normal Formal (3NF) are in 2 NF and there are no transitive
dependencies
A.Identify each new determinant
i.A determinant is any attribute whose value determines other values in a
row ( every determinant becomes a primary key for a new table)
B.Identify the dependent attributes
i.Identify the attributes that are dependent on each determinant and then
identify the dependency
ii.Name the new table to reflect its contents
C.Remove the dependent attributes from transitive dependencies
i.Remove attributes that belong to other entities
ii.Add them to the entity they belong to
 
hi Coach,
Right out of the text book from Database MAnagement class
Normal Forms
1.First Normal Form (1NF)
2.Second Normal Formal (2NF)
3.Third Normal Formal (3NF) are in 2 NF and there are no transitive
Click to expand...
You forget to mention:

BCNF, 4NF, 5NF and DKNF

Without these you may still run in update anomalies or phantom data afaik.


mfG
--> stefan <--
 
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