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How to write efficient TSQL

Over the past two months, I’ve authored a six-part blog series that delves into common errors found in SQL Server. This month, my focus has shifted towards crafting an article on T-SQL. When it comes to composing T-SQL (Transact-SQL) code, there exist a multitude of vital considerations developers should bear in mind to guarantee that their code remains efficient, maintainable, and secure.

  1. Performance Optimization:
    • Use proper indexing to speed up query execution.
    • Minimize the use of complex subqueries and functions that can slow down queries.
    • Avoid using SELECT * as it can lead to unnecessary data transfer and slow down queries.
  2. Avoid Cursors:
    • Cursors should be avoided whenever possible, as they can be slow and resource-intensive. Instead, try to use set-based operations.
  3. Error Handling:
    • Implement error handling to capture and handle exceptions gracefully using TRY…CATCH blocks.
    • Log errors and provide informative error messages for troubleshooting.
  4. Parameterization:
    • Always use parameterized queries to prevent SQL injection attacks.
    • Avoid dynamic SQL unless it’s necessary and safe.
  5. Normalization:
    • Design your database schema with proper normalization to minimize data redundancy and maintain data integrity.
  6. Transactions:
    • Use transactions to ensure data consistency and to make a series of related changes atomic (all or nothing).
  7. Code Readability:
    • Use meaningful table and column names.
    • Indent and format your code consistently to improve readability.
    • Use comments to explain complex logic or the purpose of the code.
  8. Testing and Validation:
    • Test your T-SQL code thoroughly on different data sets and scenarios.
    • Validate the results to ensure accuracy.
  9. Maintenance and Version Control:
    • Use version control systems (e.g., Git) to manage your T-SQL code.
    • Document your code and changes for easy maintenance.
  10. Data Type Selection:
    • Choose appropriate data types for your columns to minimize storage and improve performance.
  11. Plan Caching:
    • Be aware of query plan caching and the impact of parameter sniffing. Use OPTION (RECOMPILE) when necessary to force recompilation of query plans.
  12. Resource Management:
    • Be mindful of resource consumption, especially in terms of memory and CPU, when writing complex queries.
  13. Join Types:
    • Understand different join types (INNER JOIN, LEFT JOIN, etc.) and choose the appropriate one for your query.
  14. Indexes and Statistics:
    • Keep statistics updated to help the query optimizer make better decisions.
    • Monitor and manage indexes to ensure they are effective.
  15. Security:
    • Follow the principle of least privilege when granting permissions to database objects.
    • Implement role-based security and avoid using sa (system administrator) account in application connections.
  16. Scalability:
    • Design your database and queries to be scalable as data volume grows.
  17. Consistency:
    • Follow naming conventions and coding standards consistently throughout your T-SQL codebase.
  18. Monitoring and Tuning:
    • Use tools like SQL Server Profiler and Database Engine Tuning Advisor to identify performance issues and optimize queries.
  19. Documentation:
    • Document your database schema, stored procedures, and any custom functions for future reference and collaboration with other developers.
  20. Version Compatibility:
    • Be aware of the SQL Server version you are targeting and ensure your code is compatible with that version.
  21. Code Review
    • Regular code reviews provide opportunities for continuous improvement. Teams can learn from mistakes, refine their coding practices, and adapt to changes in technology and project requirements.

These considerations are essential for writing efficient, secure, and maintainable T-SQL code. Adhering to best practices and continuously improving your skills will lead to better database performance and a more robust application.

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Picture of Hemantgiri Goswami

Hemantgiri Goswami

Throughout my extensive 24-year tenure in the IT industry, I have honed my expertise in SQL Server and cloud technologies. My qualifications include certifications in ITIL, Azure, and Google Cloud, and my professional journey boasts a consistent record of delivering top-notch, dependable, and efficient solutions across diverse clients and domains. In recognition of my dedication and impact, I am honored to have received the Microsoft MVP award for SQL Server on six occasions. Additionally, I actively contribute to various online forums and blogs, acting as a moderator and facilitator of meaningful discussions. My ultimate mission revolves around empowering organizations to enhance the reliability and efficiency of their SQL Server implementations while fostering a culture of continuous learning and growth within the SQL Server community.