<aside> 💡 Database - collection of inter-related data that models some aspects of the real world

</aside>

1. Database Management System

<aside> 💡 Problems of flat files

<aside> 💡 Database Management System, DBMS

Software that allows applications to store and analyze information in a database.

A general-purpose DBMS is designed to allow the definition, creation, querying, update, and administration of databases.

Allowing programmers to focus on business problem

</aside>

Data Model → a collection of concepts for describing the data in a database.
- e.g. Relational, KV, Graph, …
Schema → a description of a particular collection of data, using a given data model.

2. Relational Model

Structure: The definition of the database's relations and their contents.
Integrity: Ensure the database's contents satisfy constraints.
Manipulation: Programming interface for accessing and modifying a database's contents.

A relation is an unordered set that contain the relationship of attributes that represent entities.
A tuple is a set of attribute values (also known as its domain) in the relation.
- Values are (normally) atomic/scalar.
- The special value NULL is a member of every domain.
A relation's primary key uniquely identifies a single tuple.
- Some DBMSs automatically create an internal primary key if a table does not define one.
A foreign key specifies that an attribute from one relation has to map to a tuple in another relation.