SAP-BI@BASICS OF DATABASE

BASICS OF DATABASE:-
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* Table.
* What is a Table?
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* Set of Rows and Coloumns.
* Coloumns would define the Logical Definetion of an entity.
* Each Row would define the physical definetion of an entity.
* Every table must have a Primary Key.
* Coloumn which can be used to maintain the Uniquness among all the records in the table - Primary Key.
* we have 2 types of coloumns in a table.
 1) Key Coloumn
 2) Non - Key Coloumn
Key Coloumn:- Coloumn which is a part of Primary Key.
Non - Key Coloumn:- Coloumn which is not a part of Primary Key.
* All Non - Key Coloumns act as Attributes or Properties for Key Coloumn.
Composite Key:-
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* When 2 or more coloumns act as the primary key of a table - Composite Key.
* Denormalized Table:-
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* Table with Redundency of data.
* Wasting Database space.
* Degarded performance.
* Normalized Table:-
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* Instead of storing the data in a single table, we split the data into multiple smaller tables connected with Primary key - Foreign Key where there is no data redundency - Normalized tables.
* Foreign Key:-
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* When a Primary key of one table takes part in the other table we call it as Foreign Key.
* Normalization:-
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* The process of converting Denomalized tables into normalized tables by using normalization forms.