📌 Concept
🔍 Intro
Data base
Relational Database
DBMS
ER basic model
Postgresql
✅ Why database is invented ?
Since the invention of the computer, we have been eager to find systems that can manage and store large amounts of structured data..
It's a tool for users to delete or post, get, patch the data. Nowadays, we can deal with the data efficiently(etc backup, safety, concurrency controle, data integrit). Every data stored into database.
⚙️ core
sort of Database
Relational Database (it also calls RDB):
- store the data as table data type.
- manupulate data through SQL
- MySQL, Postgresql,Oracle..
No SQL:
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store data as differnt type of data instead of table.
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It has flexible data structure
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MongoDB
Relation Database
there are the numerous of Database, but relational Database is the most porpular database in the world.
simple structure
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table
table for data
this is consisted with rows and cols -
cols
attribute of data
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rows
information of users
schema
schema is the blue-print defining database structure.
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table
- basic unit for storage -
column
- An attribute
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type : string boolean
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constraint : PRIMARY KEY, NOT NULL, FORERIGN KEY
DBMS(Database Management Systems)
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Database :
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System which store the data and structurise.
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storage unite for logical data
-
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Database Management Systems
- system for database
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RDB process
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writing query by Sql syntax
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user query => DBMS
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DBMS accesss/ dealing data
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return the result to user
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ER basic model
Before desigining a database, it is essential to understand the relationships between data.
At the moment, we could adopt the concept of of Entity-Relationship Model to visualize the structure of the system. This modele shows the relationships between enitity and Attribute in real world.
consistution of ER
entity
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It is independence existence to express data.
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It is mapping with table
Attribute
Attribute is unique character of entity. it is located in cols in table.
Relation
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1 to 1 relation
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An instance in enitity has a relationship with an instance in other enitity.
student---seat
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1 to many
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An instance of enitity has a relationship with several instance in other enitity.
student---major
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many to many
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instances of an enitity has a relationships with other instances of enitity.
key
- it is attribute to recognize each entity
🧩 usage of ERD
booking the seat for flights
