- Entity
- An object tracked in the Database like a Person, Place, thing etc
- Collums/Spalten
- Atrributes
- Properties or traits
- Rows/Zeilen
- Relationships
- Describes how entities interact with each other.
- Cardinalities
- Help define the relationship in a numerical context.
- Minumums and Maximuns
- Primariy Keys
- An attribute or field that uniquely identifies every record within a certain table.
- Primary Key Rules
- A primary has the be unique and identify with only only one record in our table
- It need to be never changing
- A primary key needs to be never null
- Foreign Key
- The same as a primary key, it’s just located in a foregein place.
- Unlike a primary key, a foreign key does not have to be unique. It can be repeated inside a table.
- It’s possible to have multiple foreign keys in one entity.
- Composite Primary Key
- Are used when tweo or more attributes are necessary to uniqely identify every record in a table
- Rules
- Use the feweset number of attributes as possible.
- Dont use attributes that are apt to change.
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