Study Your Answer To Question 1 Verify That The Relations Yo
Study Your Answer To Question 1 Verify That The Relations You Say
Study your answer to Question 1. Verify that the relations you say represent the Petrie’s Electronics database are in third normal form. If they are, explain why. If they are not, change them so that they are.
The E-R diagram you developed in questions in the Petrie’s Electronics case at the end of Chapter 7 should have shown minimum cardinalities on both ends of each relationship. Are minimum cardinalities represented in some way in the relations in your answer to Question 2? If not, how are minimum cardinalities enforced in the database?
Using your answer to Question 2, select data types, formats, and lengths for each attribute of each relation. Use the data types and formats supported by Microsoft Access. What data type should be used for nonintelligent primary keys?
Complete all table and field definitions for the Petrie’s Electronics case database using Microsoft Access. Besides the decisions you have made in answers to the preceding questions, fill in all other field definition parameters for each field of each table.
Paper For Above instruction
The verification of relations in a database to ensure they conform to the Third Normal Form (3NF) is a vital step in relational database design. For Petrie's Electronics database, this process begins with examining the relations derived from the Entity-Relationship (E-R) diagram and ensuring that each relation adheres to the principles of 3NF, which states that the relation is in 2NF and that all attributes are directly dependent only on the primary key.
To verify that the relations align with 3NF, one first inspects whether any non-primary key attributes depend on other non-key attributes, which would indicate transitive dependency. For example, if a relation includes attributes such as Customer Address and Customer Phone Number, and if Customer Name or ID serves as the primary key, then these attributes should depend solely on the Customer ID. Any dependency of Address or Phone Number on Customer Name suggests a transitive dependency, which violates 3NF. If such dependencies exist, the relation must be decomposed into smaller relations that isolate these attributes to eliminate transitive dependencies, thereby conforming to 3NF.
In designing the relations, it is also crucial to verify that the relations correctly represent minimum cardinalities depicted in the E-R diagram. The minimum cardinality captures the minimum number of instances of one entity that relate to an instance of another entity. In relational models, minimum cardinalities are typically enforced through constraints such as NOT NULL constraints or through application-level logic that restricts data entry. However, these are not explicitly represented in the relation schemas themselves. Instead, database constraints like NOT NULL ensure the minimum cardinality of one—to indicate that a record must exist in the related table. For instance, if each order must be associated with at least one customer, the foreign key field referencing the Customer table should be set as NOT NULL, enforcing a minimum cardinality of one.
When selecting data types, formats, and lengths for each attribute in Microsoft Access, it is essential to consider the nature of the data. Numeric data such as IDs can use the Number data type, choosing the appropriate size (Integer, Long Integer, etc.). Textual data, including names and addresses, should use the Short Text data type with appropriate field lengths—say, 50 or 100 characters depending on the expected data size. Date or time fields should utilize the Date/Time data type. For primary keys that are not integers, such as GUIDs or unique string identifiers, the appropriate data type is typically Short Text with a set length, ensuring sufficient space for unique identifiers.
To implement the database in Microsoft Access, all table and field definitions must be completed, incorporating the data types, lengths, and specific field parameters. For example, primary keys should be set as AutoNumber or Short Text depending on their nature, with the Primary Key designation applied to enforce uniqueness. Foreign keys should be set to match the data type of their primary key counterparts and often marked as NOT NULL if minimum cardinality constraints require it. Additionally, indexing can be used to improve the query performance and ensure referential integrity constraints are maintained. Field validation rules and default values should be applied where appropriate to ensure data consistency and integrity across the database.