Database Design Fundamentals

Database design encompasses several stages that collectively ensure the database meets the needs of its users and applications. These stages are

• Requirements Analysis: Understanding and documenting the requirements of the database system.
• Conceptual Design: Creating a high-level description of the database requirements.
• Logical Design: Translating the conceptual model into a logical structure using a data model like the Entity-Relationship (ER) model.
• Physical Design: Implementing the logical design into a physical database schema, including decisions on storage structures and indexing.

Requirements Analysis

The first step in database design is to gather and analyze requirements. This involves understanding what data needs to be stored, how it will be used, and the expected performance requirements. For example, consider a simple requirement: a library database system needs to store information about books, authors, and borrowers.

Example of Requirements Analysis

Consider a simple requirement: a library database system needs to store information about books, authors, and borrowers. Key activities in this stage include:

• Interviews and Surveys: Engaging with users, managers, and stakeholders to collect detailed information about their data needs.
• Document Analysis: Reviewing existing documentation, such as reports, forms, and organizational charts, to understand current data usage and flow.
• Requirement Specification: Writing detailed requirements documents that outline all data needs, including data types, relationships, constraints, and security requirements.

Conceptual Design

Once requirements are gathered, the next step is to create a conceptual design. This involves creating an abstract model of the database. Using the library example, the conceptual design might include entities like ‘Book’, ‘Author’, and ‘Borrower’, along with their relationships (e.g., each book is written by an author).

Example of Conceptual Design

Using the library example, the conceptual design might include:

• Entities: Book, Author, Member, Loan
• Attributes
  • Book: ISBN, Title, PubYear
  • Author: AuthorID, Name
  • Member: MemberID, Name, Email
  • Loan: LoanID, LoanDate, DueDate, MemberID, ISBN
• Relationships
  • A Book can have multiple Authors.
  • A Member can borrow multiple Books.
  • A Loan links a Member to a Book.

Logical Design

The logical design phase involves translating the conceptual model into a logical schema using a data model such as the Entity-Relationship (ER) model. Here, each entity and relationship is defined in detail, specifying attributes and cardinalities.

Example of Logical Design

For the library system, the logical design might involve:

• Tables:
  • Book: ISBN (PK), Title, PubYear
  • Author: AuthorID (PK), Name
  • Member: MemberID (PK), Name, Email
  • Loan: LoanID (PK), LoanDate, DueDate, MemberID (FK), ISBN (FK)
  • BookAuthor: BookID (FK), AuthorID (FK)

Physical Design

Physical design specifies how the logical design will be implemented in the database system. It involves configuring storage, indexing, partitioning, and optimizing performance. This phase translates the logical data models into actual database structures.

Example of Physical Design

For our library system, physical design might include

• Indexes: Creating indexes on ISBN, AuthorID, and MemberID for faster searches.
• Storage: Using SSDs for fast read/write operations.
• Partitioning: Partitioning the Loan table by year to improve query performance.

Database design is important for managing and organizing data effectively. It ensures data is stored efficiently, retrieved quickly, and maintained consistently. A well-designed database significantly enhances the performance and usability of applications.

In this article we will explore the basics of database design, covering key stages: requirements analysis, conceptual design, logical design, and physical design. We’ll also look at a practical example to illustrate these concepts.