How Has the Default Query Result Order Changed Between SQL Server 2008 and 2012, and What's the Best Solution?

SQL Server's Result Order: A Key Difference Between 2008 and 2012

Migrating from SQL Server 2008 to 2012 often reveals a surprising change: the default order of results from SELECT statements without ORDER BY clauses. This shift necessitates a review of existing code and strategies for maintaining data retrieval consistency.

The Solution: Explicit Ordering with ORDER BY

The most effective solution is to add ORDER BY clauses to all stored procedures lacking them. While SQL Server 2008 appeared to return rows in a consistent order, this was not guaranteed. Factors like indexing and disk storage influenced the perceived order.

SQL Server 2012's improved query optimizer and potential hardware changes result in varying execution plans, impacting the output order. Explicitly defining the desired order using ORDER BY ensures predictable results.

Understanding the Misconception of Default Ordering

The assumption that SQL results have a predetermined order without an ORDER BY clause is incorrect. Relational databases, based on set theory, treat result sets as unordered collections. The order is irrelevant; without ORDER BY, the system determines the order during optimization, and this can change.

Why Downgrading is Not the Answer

Downgrading to SQL Server 2008 might seem like a simple fix, but it's strongly discouraged. The process introduces substantial complexities and risks:

• Compatibility issues: Existing applications and data might become incompatible.
• Loss of enhancements: The numerous improvements and security features in SQL Server 2012 would be lost.
• Extensive retesting: All applications and stored procedures require thorough re-testing.

Conclusion: Embrace Best Practices

To ensure consistent and reliable results in SQL Server 2012, consistently use ORDER BY clauses. The transition from 2008 to 2012 provides an opportunity to adopt best practices and solidify understanding of fundamental SQL principles. Ignoring the order issue can lead to unpredictable behavior and potential application errors.

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