How can you debug database functions and procedures quickly?

Many people are not aware of this step through debugger in code editors like SQL Developer and Toad. They also have watch window and tooltip highlight of run time values without dedicated need to print to screen or text file.

For quick debugging of database functions and procedures: 1. Error Handling: Implement thorough error handling to catch and log exceptions. 2. Logging:Use logging to record key info like input, variables, and flow. 3. Print Statements: Insert prints to output variable values and checkpoints. 4. Step-Through:Utilize a debugger to inspect variable values step by step. 5. Check Input/Output:Validate inputs and confirm expected outputs. 6. Simplify Data: Test with minimal, verifiable input to isolate issues. 7. Use Debugging Tools:Leverage DBMS tools like query plans. 8. Review Logic:Break down complex operations for review. 9. Consult Docs:Refer to DBMS docs for debugging guidance. 10. Collaborate: Discuss the problem with peers for insights.

SQL Server has a debugger feature in SQL Server Management Studio, Oracle has a debugger tool in SQL Developer, and MySQL has a debugger plugin in MySQL Workbench. Using a debugger tool can help you identify where and why your code is failing, and test different scenarios and inputs

I use PL/SQL Developer for debugging almost everyday and I find this application very useful, so I can recommend it. The built-in debugger is quite user friendly. You can debug not only stored procedures, but also anonymous PL/SQL code blocks. And you can run queries during debug sessions so you can see the actual data changes in tables and not only variables’ values.

Here are some strategies and best practices to debug database fun/proc: Built-in Debuggers: Oracle and MS SQL Server provides tools to step through proc/fun, this allows to inspect set the breakpoints. Print Statements: PRINT statements can help understand the flow of fun/proc and the values of variables at different points. Temporary Tables: We can use temp tables to store intermediate results. This will allow us to examine the data at various stages of the fun/proc. Version Control: Being able to roll back to a previous version or compare changes can be invaluable when trying to track down a bug. Exception Handling: When an error occurs, we can provide meaningful error messages. Consistent Formatting for the code is also very important.

In addition to print statements there may be scenarios that you cannot run a part of code independently and may have to rely on front-end application and or other units due to bad design then limited option would be to log the messages to file system on database server. Use your standard file output to log messages in text file.

Using debugger tool provided by the database side, passing the messages and format_error_backtrace etc. For example : In Oracle dbms_debug Connect sessions privilege is requires

I think it is important to use logs and print statements but I also think there should be an investment into debugging. Often, developers will use temporary tables to mitigate data. For me, it’s important to see what is being added to those tables. Sometimes this can be achieved by a simple select from the temporary table. But another method is selecting the output into a table on your database so the results can be recalled via query. The output to the table can be stored as json in a single column to save on space (should the environment be a smaller environment)

You can have proper documentation in code header to include debugging code with sample data and code. Also, ensure each function or procedure only does 1 job and code is modular with high cohesion and low coupling. Most cases code is not testable and maintainable due to missing this simple design principle, high cohesion and low coupling.

Also, you can have constraints designed in database and tie those with exceptions in pragma init to have proper user friendly error messages. Exception handler should be from most specific to most generic one. This is just 1 challenge other challenge is use this exception handling to publish proper error messages. Always stick to strategy, exceptions should be handled gracefully, very near to place where exception occurred, manage it by logging, commit/ rollback and decide whether to propogate to parent and see how to recover the application from error. Generic exception handlers should be last resort and only for unhandelled exceptions, but still see logging and publishing maximum information for support team to work on.

Step by step debugging even when there is no error helps in identifying any wrong assumption or less optimal execution path or bad algorithm design. It is always advisable to divide your code into small manageable units and step through it to confirm algorithm design.

Version Control: Maintain a version control system for your SQL code. This allows you to revert to previous working versions if debugging efforts fail or if new issues arise during the process. Step-by-Step Execution: Break down complex SQL queries into smaller, manageable parts. Execute and debug these sections step by step, verifying the output at each stage. This approach simplifies issue detection and resolution. Structured Approach: Start with a structured and organized coding style. Use consistent indentation, naming conventions, and commenting to make your code readable and maintainable. This helps in identifying issues quickly.

For future reference, think about documenting all of the troubleshooting, results, and insights. It contributes to preserving knowledge and making it accessible to others who might need it in the future. Additionally, it promotes openness and information exchange within a group or organisation.

Use OEM: If you have access to Oracle Enterprise Manager ( OEM) you can use it to monitor and capture any bind values passed to the sqls inside the functions and procedures. If you don't have access to OEM ask your DBA to monitor and capture the sqls that are taking longer and each query it ran under your session while you execute the function/procedure.