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name: database-schema-design description: A guide for relational database schema design best practices. Use this skill when a user wants to design a new database schema, understand best practices, create an ERD, write DDL scripts, or develop an indexing or schema evolution strategy.

Relational Database Schema Design

This skill provides a structured workflow for designing robust and scalable relational database schemas.

Schema Design Workflow

Follow these steps to design a database schema. For detailed principles and best practices for each step, consult the Design Principles Guide.

1. Identify Entities & Attributes: Analyze requirements to find the core nouns (entities) and their properties (attributes).
2. Determine Relationships: Define how entities relate to each other (one-to-one, one-to-many, many-to-many).
3. Create an ERD with Mermaid: Visualize the schema with an Entity-Relationship Diagram.
4. Define Constraints: Specify rules to ensure data integrity (primary keys, foreign keys, unique, check).
5. Generate DDL Scripts: Write the SQL code to create the schema.
6. Develop Indexing Strategy: Plan indexes to optimize query performance.
7. Consider Denormalization: Decide if and where to denormalize for performance reasons.
8. Plan for Schema Evolution: Establish a strategy for managing future schema changes.

ERD Creation Guide with Mermaid

Use Mermaid syntax to create an ERD. This provides a clear, version-controllable diagram of the schema.

Example: A simple blog schema.

CopyerDiagram
    USER {
        int id PK "User ID"
        string name "User's full name"
        string email "Unique email"
    }
    POST {
        int id PK "Post ID"
        string title "Post title"
        string content "Post body"
        int user_id FK "Author of the post"
    }
    USER ||--|{ POST : "writes"

Cardinality Syntax:

• |o--|| : One-to-one
• |o--|{ : One-to-many
• }o--|{ : Many-to-many

Additional Resources

• Core Design Principles: Detailed guide on entities, relationships, attributes, constraints, and denormalization.
• SQL DDL Templates: Reusable SQL templates for creating tables, constraints, and other schema objects.
• Indexing Checklist: A checklist to guide your indexing strategy for optimal performance.
• Schema Evolution Strategy: A document on how to manage changes to your database schema over time.