Which Database Design Best Manages Employee Revisions: XML, Duplication, or Audit Trail?

Comparing Database Designs for Employee Revision Management

Effective revision management hinges on a well-designed database. Let's weigh the pros and cons of three common approaches to storing employee revisions: XML storage, field duplication, and audit trails.

Approach 1: XML-Based Revision Storage

• Benefits: Compact storage of extensive historical data.
• Drawbacks: Slower data access due to XML parsing. Limited data manipulation and reporting capabilities because joins on revision fields aren't readily available.

Approach 2: Duplicating Employee Data in a Revisions Table

• Benefits: Fast data access; no XML parsing needed. Supports joins and complex queries on revision fields.
• Drawbacks: Significant data duplication across all entities, potentially leading to substantial storage overhead.

Approach 3: The Audit Trail Table

A robust alternative is an audit trail table, structured as follows:

<code>[ID] [int] IDENTITY(1,1) NOT NULL,
[UserID] [int] NULL,
[EventDate] [datetime] NOT NULL,
[TableName] [varchar](50) NOT NULL,
[RecordID] [varchar](20) NOT NULL,
[FieldName] [varchar](50) NULL,
[OldValue] [varchar](5000) NULL,
[NewValue] [varchar](5000) NULL</code>

• Benefits: Tracks all changes across various entity types. Provides a detailed change history for granular tracking. Avoids data duplication by centralizing change records. Offers fast query and data retrieval.
• Drawbacks: Potential performance impact on frequently updated databases. Requires extra triggers and maintenance to ensure accurate revision capture.

Choosing the Right Approach

The optimal design depends on project-specific needs:

• Infrequent reporting and human-readable history: XML storage might suffice.
• Rapid data access and complex queries: Field duplication provides better performance.
• Comprehensive revision tracking across multiple entities: An audit trail table offers scalability and flexibility.

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