DB theoretical part

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Database(DB) - organized collection of related data that are electronically stored and used.

Database management systems(DBMS) - software system that provides users a function that defines, creates, and manages DB.

For example, PostgreSql, MySql...

When defining DB, extra data occurs -> metadata (data about data)

Database system - DB + DBMS + related applications


Data models - provides a method that expresses DB structure abstractly.

Data models' different types




Database Schema - description of the structure of database based on data model. It usually doesn't change after being decided




Before diving into relational database, let's check where "relational" came from.

"Relational" comes from mathematics. 

What is "Set"? Set - collections that have different elements and the order of elements doesn't matter.



relation in mathematics -> subset of Cartesian product, set of tuples

Relational data model









Relation schema - relation names : attributes list

Degree of a relation - the number of attributes in relation schema

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