what is difference between normalization and denormalization. in normalizatio

what is difference between normalization and
denormalization.
in normalization all tables are normalizad format or not.
what r the types of indexes are there.
what is difference b/w bitmap,b-tree,unique and function
based indexes.

Question Posted / srinivas

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what is difference between normalization and denormalization. in normalization all tables are nor..

Answer / karthikeyan

Denormalization is the process of attempting to optimize the
performance of a database by adding redundant data or by
grouping data.
Normalization is the process of de-composing a relation with
anomalies into a well structured relation.

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what is difference between normalization and denormalization. in normalization all tables are nor..

Answer / samarth

Denormalization is the process of introducing redundancy
into a table by incorporating data from a related table.
Tables are usually denormalized to prevent expensive SQL
join operations between them.

One should always normalize to third-normal form and only
apply denormalization selectively as a last resort if
performance problems are experienced. Remember that
denormalizations is not free and introduces the following
problem into the design:
More disk space is used as the same data is duplicated in
more than one table
DML operations are more expensive as the same data must be
maintained in more than one table
You run the risk that the data can get "out of sync"