Chapter 4: Relational Databases

Chapter 4: Relational Databases

1. Relational Models

   • Relational databases store information in the from of related two- dimensional table. Relationships can be added as needed making it the best option in modern times.
   • Entities
     • Entities are Classes. They consist of resources, events, and agents.
     • Attributes
       • Attributes are characteristics, properties, or adjectives that describes each class. Each attribute must have a unique name. The values of a specific attribute must be of the same type: alpha, numeric, etc. All non-key attributes must describe a characteristic of the class identified by the PK.
   • Constructs
     • Constructs are what make up the database.
     • Tables
       • The primary construct to store data.
       • Columns = Fields
         • The vertical divisions of a table. They represent the attributes of the class or the relationship. Each attribute/column of a record must be single-valued. Requires a relationship table for each many-to-many relationship
       • Rows = Records=Tuples
         • The horizontal divisions in a table. They represent the specific data values associated with one instance.
   • Relationships
     • Logical relationships are created between tables using keys.
     • Primary Key: Entity Integrity Rule
       • (PK) Primary Keys are unique identifiers for a specific row. They cannot be null which is the Entity Integrity Rule.
     • Foreign Keys: Referential Integrity Rule
       • (FK) Foreign Keys can be null or they can be the primary Key of another table/row. Known as the referential integrity rule.
   • ACCESS: Understanding how to use.
     • Access is one way to create a relational database. It is composed of seven objects used in implementation: Queries, Forms, Reports, Pages, Macros, Modules, and Subjects.
     • SQL: Structured Query Language
       • (Phonetic) Sequel is a computer language designed to query data in a relational database and is based on relational algebra. It is the basis of all queries one will use to retrieve information.
       • SELECT:
       • FROM:
       • WHERE:
       • GROUP BY:
     • CREATE A DATABASE: BEGINNERS
       • This video shows how to set up and save a basic database by creating tables, fields,  records, and forms. It shows how to import from excel, make a query, and a report. Time Stamps: create and save: 1:21 Table: 6:45 Field: 8:30 Records 10:53 Import from Excel 12:52 Form 15:16 Design View 16:15 Enter or Modify 18:20 Query 20:25 Modify Query 22:02 Report 23: 59
     • Query 1 Table
     • Query Multiple Tables
     • 15 Query Examples

2. 2. Network Models

   • Network Models are more flexible than Hierarchical Models. There can be  multiple parent and multiple child relationships. This results in M:N  mapping meaning many-to-many.

3. 1. Hierarchical Models

   • Hierarchical Data Models were the primary models used widely in mainframe database management. Their organization forms a family tree of parent/child relationships. They have 1:N mapping meaning one-to-many relationship

Bilder und Dateien der Mindmap

• Microsoft Access Tutorial - Beginners Level 1 (Quick Start) (Einbetten)
• Access: Multi-table Queries (Part 1) (Einbetten)
• Access: Designing a Simple Query (Einbetten)
• Office 2016 Video #40: Access 2016: Building Queries in Access (15 Examples) (Einbetten)