Normalization

Normalization

Normalization is the Process of Organizing the  data in an efficient manner.Really Normalization evolves from the Database optimization perspective.Really a good Database design solves the 30 % of the Database Performance Issues.IT reduce redundancy of Data.Normally we are doing

3 levels of normalization

First Normal Form (1NF)

First normal form (1NF) sets the very basic rules for an organized database:

  • Eliminate duplicative columns from the same table.
  • Create separate tables for each group of related data and identify each row with a unique column or set of columns (the Primary key).

Second Normal Form (2NF)

Second normal form (2NF) further addresses the concept of removing duplicative data:

  • Meet all the requirements of the first normal form.
  • Remove subsets of data that apply to multiple rows of a table and place them in separate tables.
  • Create relationships between these new tables and their predecessors through the use of foreign Keys.

Third Normal Form (3NF)

Third normal form (3NF) goes one large step further:

  • Meet all the requirements of the second normal form.
  • Remove columns that are not dependent upon the primary key.

Difference Between Union all and Union

Many People know answer for this , but some people are there who are new into this,

What is UNION?

UNION is used to join two related set of data.UNION will give a distinct result ie; it

will avoid duplicates.How ever  the UNION  is bit slower due to distinct sort.

UNION

What is UNION ALL

UNION ALL is also used to join two related set of data.UNION ALL will not Provide  a distinct sort.So it is very fast than UNION

UNION ALL