Database normalization is a technique for designing
relational database tables to minimize duplication of
information and, in so doing, to safeguard the database
against certain types of logical or structural problems,
namely data anomalies.
For example, when multiple instances of a given piece of
information occur in a table, the possibility exists that
these instances will not be kept consistent when the data
within the table is updated, leading to a loss of data
integrity. A table that is sufficiently normalized is less
vulnerable to problems of this kind, because its structure
reflects the basic assumptions for when multiple instances
of the same information should be represented by a single
instance only.
Note:
1. data is normalized in oltp systems
( are of different forms :1NF, 2NF, 3NF, BCNF, 4NF,
5NF,DKNF,6NF)
2. when it comes to olap/datawarehouse/dss sytems data is
generally de-normalized. (N1NF, PNF).
there is always a trade-off to consider between data
redundancy vs performance
Database normalization is a process in which data in a
single table is being replaced into number of tables with
the same data along with some key relationships being set
up among the tables.
Normalization is the process of braking down one table into
more than one tables so that data redudancy can be removed.
There are some rules to perform Normalization are called
Normal Forms.
There is a big table with "n" of rows and 40 + columns .It
doesn't have primary key.How do you select the primary key.
In other words how do you get the duplicate records.
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