How Can I Efficiently Audit Historical Data Changes in SQL Server While Maintaining Performance?

Auditing Historical Changes in SQL Server: A Comprehensive Guide

Question:

How to effectively store and track historical changes in a database while maintaining performance and flexibility?

Background:

Your system consists of two tables: Table-A, which contains current data rows, and Table-A-History, which stores historical data. You need to ensure that the most recent row is always in Table-A, while preserving historical data in Table-A-History.

Methods and Performance Considerations:

Method 1: Move Current Rows from Table-A to Table-A-History

When a new data row becomes available, move the existing current row from Table-A to Table-A-History. Then, update Table-A with the new data.

Advantages:

• Maintains a small and efficient Table-A.
• Minimal index overhead in Table-A.

Disadvantages:

• Requires additional inserts and deletes.
• Joins are necessary for historical reporting.

Method 2: Update Table-A and Insert New Row into Table-A-History

When a new data row becomes available, update the existing row in Table-A and insert a new row into Table-A-History.

Advantages:

• Historical reporting is straightforward without joins.

Disadvantages:

• Table-A can become large with increasing historical data.
• Index overhead in Table-A can be significant.

Additional Solutions to Consider:

• Auditing with Triggers: Use triggers to capture DML (insert, update, delete) changes and store them in a separate audit table.
• Effective Dating: Mark rows as inactive instead of deleting them, creating a type 2 slowly changing dimension (SCD).
• Change Data Capture (Enterprise Feature): Capture data changes using the CDC feature, which logs changes but may not provide enough information.
• Change Tracking (All Versions): Track changes in SQL Server tables but comes with limitations for auditing purposes.

Recommendation:

The best method depends on specific requirements and performance constraints. If you need minimal table size and index overhead, Method 1 with an audit table may be suitable. For easy historical reporting, Method 2 with effective dating could be a good choice.

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