====== LU04a - Concept of a RDB ======

==== Learning Objectives==== 
  - I can explain in my own words, what a relations database is and why it is widely used in all kinds of web applications.
  - I can name and explain the key components of a relational database.


A Relational Database (RDB) is a structured method for storing and organizing data. The core idea is to represent data as related tables.

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==== Key components ==== 
  * **Tables**: A collection of related data organized into rows (records) and columns (fields). Each row represents a unique entity, and columns contain specific attributes.
  * **Records**: A single row in a table, representing a specific instance of data.
  * **Fields**: A column in a table, defining the type of data stored in each row.
  * **Relationships**: Connections between tables based on shared data. Common types include one-to-one, one-to-many, and many-to-many relationships.

==== Structure and Integrity ====
  * **Primary Key**: A unique identifier for each record in a table.
  * **Foreign Key**: A field in one table that references the primary key in another table, establishing a relationship.
  * **Data Integrity**: Ensures data accuracy and consistency through constraints like:
    * Entity Integrity: Every table must have a primary key with no null values.
    * Referential Integrity: Foreign key values must match existing primary key values or be null.
    * Domain Integrity: Data values must conform to defined data types.

==== Advantages of RDBs ===
  * **Data Consistency**: Enforced by relationships and constraints.
  * **Data Security**: Access control mechanisms protect sensitive information.
  * **Data Independence**: Changes to data structure can be made without affecting applications.
  * **Efficient Data Access**: Indexing and query optimization enhance performance.

==== Common RDB Systems ====
  * MySQL
  * PostgreSQL
  * Oracle Database
  * Microsoft SQL Server

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===== Vocabulary =====
^ English ^ German ^
| row | Zeile |
| column | Spalte | 
| entity | Objekt(-Einheit) |
| attribute | Eigenschaft |
| instance | Exemplar, Beispiel |
| unique | einzig(-artig) |
| to reference to | verweisen auf |
| to establish | errichten, herstellen | 
| consistency | Widerspruchsfreiheit, Übereinstimmung | 
| constraint | Auflage, Bedingung |
| to enhance | verbessern, aufwerten |

===== References =====
Definition RDB: https://de.wikipedia.org/wiki/Relationale_Datenbank

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{{tag>M290-LU03}}
[[https://creativecommons.org/licenses/by-nc-sa/4.0/|{{https://i.creativecommons.org/l/by-nc-sa/4.0/88x31.png}}]] Volkan Demir