T-sql Cast versus Convert

Efficiency and compatibility: Unpacking the power of CAST and CONVERT

CAST is your reliable, ANSI-SQL standards compliant buddy, performing quick-n-easy conversions across nearly all SQL systems — a universal translator in the world of SQL.

SELECT CAST('42' AS INT); -- Hitchhiker’s Guide to SQL, anyone?
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On the other hand, CONVERT is like the cool kid on the SQL Server block offering extra formatting prowess and extra cool points with its style parameters for datetime conversions.

SELECT CONVERT(VARCHAR, GETDATE(), 112); -- Date’s new secret code name: YYYYMMDD
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But before you choose sides, remember: performance may vary! Run a benchmark test suiting your data types and operations for the most optimal results.

Introducing potential pitfalls: Logic traps and workarounds

Implicit conversions: A sticky wicket

Implicit conversions are like chameleons- blending in comfortably but potentially dangerous when unnoticed. They can lead to unexpected results and performance slowdowns.

• Get ahead of them with explicit CAST or CONVERT for preventing loss of precision.

  DECLARE @temp AS VARCHAR = '89.923';
  SELECT CAST(@temp AS DECIMAL(5,2)); -- Returns 89.92
  SELECT CONVERT(DECIMAL(5,2), @temp); -- Accurate to the last penny
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• Stay vigilant with tools for identifying implicit conversions that might need optimizations.

Picking the right tool for the job

• Use CAST when converting data types among multiple SQL platforms and for simple type transformations without particular format requirements.

• Go for CONVERT when format specifications are key, such as datetime conversions, complex expression handling and the times when extra readability can make all the difference.

Best practices and resources: The wherefores and whys

Precision and performance

Striking a balance between CAST and CONVERT will depend on your specific needs:

• CAST for predictability and ensuring portability.
• CONVERT for SQL Server-specific functionalities, formatting needs, and cultural settings.

Continual learning: Leveraging resources

Utilize the treasure trove of official guides and practical examples online:

• The MSDN documentation offers comprehensive guidelines on using CAST and CONVERT.
• The SQL Server Data Type Conversion Chart helps you understand the convertible data types, preventing incompatible conversions.

Real-world applications

• Formatting dates and times for international standards or specific formats.
• High-precision calculations in finance, where rounding can have significant impacts.