Unterschiede
Hier werden die Unterschiede zwischen zwei Versionen angezeigt.
| Beide Seiten der vorigen Revision Vorhergehende Überarbeitung Nächste Überarbeitung | Vorhergehende Überarbeitung | ||
| modul:m290:learningunits:lu03:theorie:d_crowfeet [2024/08/16 10:49] – vdemir | modul:m290:learningunits:lu03:theorie:d_crowfeet [2024/10/02 15:14] (aktuell) – vdemir | ||
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| - | ====== | + | ====== |
| - | ===== The Basics of Crow’s Foot Notation | + | ==== The Basics of Crow’s Foot Notation ==== |
| In database design, an **entity** represents a real-world object or concept, such as a person, place, event, or thing, that needs to be stored in the database. Each entity typically becomes a table in the relational database. **Attributes** of the entity, which are the data points relevant to that entity (like a customer’s name or an order’s date), become the columns in these tables. | In database design, an **entity** represents a real-world object or concept, such as a person, place, event, or thing, that needs to be stored in the database. Each entity typically becomes a table in the relational database. **Attributes** of the entity, which are the data points relevant to that entity (like a customer’s name or an order’s date), become the columns in these tables. | ||
| Crow’s Foot notation focuses primarily on the relationships between these entities. It visually conveys how entities are related to one another and the cardinality of these relationships, | Crow’s Foot notation focuses primarily on the relationships between these entities. It visually conveys how entities are related to one another and the cardinality of these relationships, | ||
| - | ===== Cardinality in Crow’s Foot Notation | + | ==== Cardinality in Crow’s Foot Notation ==== |
| Cardinality describes the nature of the relationship between two entities and is typically categorized as: | Cardinality describes the nature of the relationship between two entities and is typically categorized as: | ||
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| 3. **Many-to-Many (M:N):** This relationship implies that multiple instances of entity A can be related to multiple instances of entity B. For example, students and courses have a many-to-many relationship because each student can enroll in multiple courses, and each course can have multiple students enrolled. In Crow’s Foot notation, this relationship is shown with a " | 3. **Many-to-Many (M:N):** This relationship implies that multiple instances of entity A can be related to multiple instances of entity B. For example, students and courses have a many-to-many relationship because each student can enroll in multiple courses, and each course can have multiple students enrolled. In Crow’s Foot notation, this relationship is shown with a " | ||
| - | The image below shows all possible cardinalities between entities. | + | The figure |
| - | {{: | + | {{: |
| - | ===== Why Use Crow’s Foot Notation? ===== | + | [[https:// |
| + | ==== Why Use Crow’s Foot Notation? ==== | ||
| Crow’s Foot notation is favored for its clarity and ease of understanding. Its visual symbols are intuitive and make it easy to quickly grasp the nature of relationships between entities. This simplicity is particularly valuable when communicating database designs to stakeholders who may not be experts in database design but need to understand the overall structure and how data interrelates. | Crow’s Foot notation is favored for its clarity and ease of understanding. Its visual symbols are intuitive and make it easy to quickly grasp the nature of relationships between entities. This simplicity is particularly valuable when communicating database designs to stakeholders who may not be experts in database design but need to understand the overall structure and how data interrelates. | ||
| - | + | ==== Example of Crow’s Foot Notation | |
| - | + | ||
| - | ### Example of Crow’s Foot Notation | + | |
| Consider a simple ERD for an online bookstore. The entities might include **Customers**, | Consider a simple ERD for an online bookstore. The entities might include **Customers**, | ||
| - | - **Customers** can place multiple **Orders** (One-to-Many). | + | * **Customers** can place multiple **Orders** (One-to-Many). |
| - | - Each **Order** can include multiple **Books** (Many-to-Many). | + | |
| Using Crow’s Foot notation: | Using Crow’s Foot notation: | ||
| - | - The relationship between **Customers** and **Orders** would have a single line connecting the entities with a vertical line on the **Customers** side and a crow’s foot on the **Orders** side. | + | * The relationship between **Customers** and **Orders** would have a single line connecting the entities with a vertical line on the **Customers** side and a crow’s foot on the **Orders** side. |
| - | - The relationship between **Orders** and **Books** would have crow’s feet on both sides, representing the many-to-many relationship. | + | |
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| - | ### Conclusion | + | |
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| - | Crow’s Foot notation is a powerful tool in the design and representation of relational databases. By visually capturing the relationships and cardinality between entities, it simplifies the process of database design, ensuring that data structures are well-organized and accurately reflect the complexities of real-world relationships. Understanding and applying Crow’s Foot notation is essential for anyone involved in the creation or management of relational databases, as it promotes both efficiency and clarity in database design. | + | |
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| - | ===== Assignments ===== | + | |
| - | + | ||
| - | <nspages .:aufgaben -h1 -exclude: | + | |
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| - | ===== Vocabulary ===== | + | |
| - | + | ||
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| - | + | ||
| + | ==== Vocabulary ==== | ||
| + | ^English ^ Deutsch ^ | ||
| + | | to convey | vermitteln, mitteilen | | ||
| + | | to refere to | Bezug nehmen auf | | ||
| + | | instance | Beispiel | | ||
| + | | nature | Wesen, Beschaffenheit | | ||
| + | | to indicate | andeuten, zeigen | | ||
| + | | might | möglicherweise | | ||
| + | | to denote | bedeuten, hindeuten | | ||
| + | | to depict | darstellen | | ||
| + | | to imply | implizieren | | ||
| + | | to enroll | einschreiben, | ||
| + | | to consider | in Betracht ziehen, bedenken | | ||
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| [[https:// | [[https:// | ||