Basic database terminology

                                     Relational schema 

                   an existing idea of how the DB must be organized

Primary key : A column(or set of columns) whose value exists and is unique for every record in a table is called primary key.


Foreign Key :  Identifies the relationship between tables,not the tables themselves.


Unique Key & Null values : Used whenever you would like to specify that you don't want to see duplicate data in a given fields.

Example :

Relationships : Relationships tell you how much of the data from the foreign key field can be seen in the primary key column of the table the data is related to and vice-versa.


One to Many Relation : 


Example : of ONE  toooooo

MANY:


Many to One :





 


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