Convert The Data Model You Constructed For Queen Anne Cup
Convert the data model you constructed for the Queen Anne Curiosity Shop in part D at the end of Chapter 4 into a relational database design
Develop a relational database design based on the provided Entity-Relationship (E-R) diagram for the Queen Anne Curiosity Shop. Specify tables, primary keys, foreign keys, and other relevant column properties as per the instructions. Describe how you have represented weak entities, supertype and subtype entities, if applicable, and clarify the structure of each table with column data types, key constraints, required fields, default values, and remarks or comments to elucidate surrogate key usage or other notable features.
Paper For Above instruction
The process of transforming an entity-relationship (E-R) diagram into a relational database schema is fundamental in database design, especially when applied to a business context such as the Queen Anne Curiosity Shop. This transformation involves systematically mapping entities, relationships, and constraints into relational tables, ensuring data integrity, normalization, and efficient data retrieval.
Entities and their Tables
The primary entities identified from the E-R diagram include CUSTOMER, EMPLOYEE, VENDOR, SALE, SALE_ITEM, ITEM, and ORDER. Each entity becomes a table in the relational schema, with primary keys (PK) uniquely identifying each record. For example, the CUSTOMER table includes columns such as PersonID (PK), LastName, FirstName, Address, City, State, ZIP, Phone, and Email, with PersonID set as the surrogate key (auto-incremented integer), ensuring consistency across related tables.
Handling Weak Entities
Weak entities lack sufficient attributes to form a primary key independently and depend on a related owner entity. For instance, if SALE_ITEM is such a weak entity, its primary key comprises its own identifier (SaleItemID) combined with the foreign key referencing the SALE table (SaleID). This relationship is enforced via foreign key constraints with cascade updates/deletes where appropriate, to maintain referential integrity. The SALE_ITEM table's columns include SaleItemID (PK, surrogate), SaleID (FK), ItemID (FK), Quantity, ItemPrice, and ExtendedPrice, with Required attributes specified for necessary fields.
Supertype and Subtype Entities
Supertype entities represent generalized categories, whereas subtypes capture specific roles. If such an entity exists — for example, PERSON serving both CUSTOMER and EMPLOYEE roles — inheritance can be modeled via a PERSON table with common attributes such as PersonID (PK), LastName, FirstName, Address, etc. Subtype tables (e.g., CUSTOMER or EMPLOYEE) extend PERSON through foreign keys and include subtype-specific attributes like CreditCardType or HourlyPayRate. This approach supports polymorphism and maintains normalization, with constraints ensuring each person holds at most one subtype role.
Column Properties and Data Types
- Primary keys are designated with the Key attribute, typically integer or surrogate keys with auto-increment. For example, PersonID in PERSON is an integer PK.
- Foreign keys reference primary keys of related tables, establishing relationships, such as SaleID in SALE_ITEM referencing SALE.
- Columns are marked as Required if null values are not permissible, such as ItemID in SALE_ITEM.
- Default values, like a default 0 for Quantity, are specified where appropriate.
- Remarks include notes on surrogate key generation, data constraints, or special considerations such as using VARCHAR for textual data and DECIMAL for currency or precise measurements.
Example Table Specification
| Table Name | Column Name | Data Type | Key | Required | Default Value | Remarks |
|---|---|---|---|---|---|---|
| CUSTOMER | PersonID | INT | PK | YES | AUTO_INCREMENT | Surrogate primary key for customer |
| CUSTOMER | LastName | VARCHAR(50) | YES | |||
| EMPLOYEE | PersonID | INT | PK | YES | AUTO_INCREMENT | Surrogate primary key for employee |
| VENDOR | VendorID | INT | PK | YES | AUTO_INCREMENT | |
| SALE | SaleID | INT | PK | YES | AUTO_INCREMENT | |
| SALE_ITEM | SaleItemID | INT | PK | YES | AUTO_INCREMENT | Surrogate primary key; dependent on SaleID |
| SALE_ITEM | SaleID | INT | FK | YES | References SALE(SaleID) | |
| SALE_ITEM | ItemID | INT | FK | YES | References ITEM(ItemID) |
Summary of Relationships
Relationships such as SALE containing SALE_ITEM, VENDOR supplying ITEM, and PERSON playing roles as CUSTOMER or EMPLOYEE are implemented via foreign keys. These relationships enforce referential integrity and support join operations necessary for queries involving sales, inventory, and personnel data. Constraints, such as cascade delete or update policies, are applied based on the business rules to preserve data consistency across related tables.
Conclusion
Transforming the E-R diagram of the Queen Anne Curiosity Shop into a relational schema requires careful consideration of entity dependencies, inheritance structures, and relationship constraints. Using surrogate keys, appropriate data types, and foreign key relationships ensures a normalized, scalable, and maintainable database design that accurately reflects the shop’s data model. This relational schema facilitates efficient data management for operations such as sales tracking, inventory control, and personnel management, supporting the business's informational needs.
References
- Ceri, S., & Widom, J. (1990). Deriving Relations from Entity-Relationship Schemas. ACM Transactions on Database Systems (TODS), 15(2), 186–214.
- Elmasri, R., & Navathe, S. B. (2015). Fundamentals of Database Systems (7th ed.). Pearson.
- Date, C. J. (2012). Database Design and Relational Theory: Normal Forms and Equivalent Decompositions. O'Reilly Media.
- Hoffer, J. A., Ramesh, V., & Topi, H. (2016). Modern Database Management (12th ed.). Pearson.
- The Data Warehouse Toolkit: The Definitive Guide to Dimensional Modeling. Wiley.
- Zhou, Y., & Yang, H. (2017). Structural Representation of Database Schemas: From ER Diagram to Relational Schema. Procedia Computer Science, 107, 798–805.