Relational Database Creation

The relational database for the purchase and payment process is built using the structure defined by the UML class diagram. This diagram, developed earlier in the modeling stage, becomes the blueprint for creating the tables and relationships in the database.

Key Steps in the Implementation Process

1. Tables and Attributes: Each class from the UML diagram is translated into a relational database table. The attributes of the class become the fields within the table. For example, a Purchases table will include attributes like purchase order number, purchase order date, and supplier information.

2. Primary and Foreign Keys: Primary keys uniquely identify each record in a table. Foreign keys are used to create relationships between tables, linking them according to the associations defined in the UML diagram. For example, a Supplier_Number might serve as a foreign key in the Purchases table to link it to the Suppliers table.

3. Handling Many-to-Many Relationships: In cases where there are many-to-many relationships, such as between purchases and products, an intermediary or junction table (e.g., PurchaseItems) is created. This table would store details of each purchase, including the product, quantity, and price.

4. Foreign Key Allocation: To manage these relationships, foreign keys are allocated appropriately to ensure that the database reflects the structure of the UML model. For example, Product_Number in the PurchaseItems table will link back to the Products table.

Data Integrity and Referential Integrity: Enforcing referential integrity ensures that all relationships between tables remain consistent. This involves ensuring that foreign key values in a table correspond to primary key values in another related table, preventing orphan records or invalid references.