Basics of Database Part 02

-

 Normalization


- Decompose larger, complex table into simpler and smaller ones.

- Moves from lower normal forms to higher normal forms.


Normal Forms


- First normal form (1NF)

- Second normal form (2NF)

- Third normal form (3NF)

- Higher normal form (BCNF, 4NF, 5NF)


Need of Normalisation


- In order to produce good database design.

- To ensure all database operations to be efficiently performed.

- Avoid any expensive DBMS Operations.

- Avoid unnecessary replication of information.


Functional Dependency Types


- Partial functional Dependency

- Transitive Dependency


First normal form (1NF)


- All attributes in the relation are atomic (indivisible value)

- There are no repeating elements or group of elements


Second normal form (2NF)


- A relation is said to be in 2NF  if and only if it is in 1st normal form

- No partial dependency exists between non key attributes and key attributes.


Third normal form (3NF) 


- It is in 2NF. no transitive dependency exists between non key attributes and key attributes through another non key attributes.


What is SQL?


Programming language specifically designed for working with database to

- Create

- Manipulate

- Share/ Access


Why SQL?


- Allows users to communicate i.e. access and manipulate the database

- Allows users to retrieve data from database

- Allow users to create, update, modify and delete the database.


SQL Terms


Data: Data is defined as facts or figures or information that's stored in or used by a computer.


Database: A database is a organised collection of data/ Information so that it can be easily accessed managed and updated.


SQL Data Types


Numeric: bit, tinyint, smallint, int, bigint, decimal, numeric, float, real.


Character/ String: char, varchar, text


Date/Time: Date, Time, Datetime, Timestamp, Year.


Miscellaneous: Json, XML


SQL Constraints


Not Null: Ensures that a column does not have null value.


Default: Provides a default value for a column when none is specified.


Unique: Ensures that all the values in a column are different.


Primary: Identifies each row/ record in a database table uniquely.


Check: Ensures that all values in a column satisfy certain conditions.


Index: Create and retrieves data from the database very quickly.


 #design #sql #data #share #database #programming #language #day2


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