DELIMITER $$
CREATE PROCEDURE GetEmployeeByDepartment(IN dept_id INT)
BEGIN
    SELECT name, position, salary 
    FROM employees 
    WHERE department_id = dept_id;
END $$

DELIMITER ;

CALL GetEmployeeByDepartment(3);

Understanding the Execution Flow:

• The CREATE PROCEDURE statement defines the procedure.
• The CALL statement triggers its execution.
• The result of the SELECT query inside the procedure is returned to the caller.

Pros of Using Stored Procedures in MySQL

1. Performance Improvement

Stored procedures help optimize performance by reducing the amount of data transferred between the application and the database. Instead of sending multiple queries, a single call to a stored procedure can execute a series of SQL statements on the server, reducing network overhead.

2. Code Reusability

Once a stored procedure is created, it can be reused multiple times by different applications or queries. This makes the code more maintainable and reduces the chances of errors caused by duplicate SQL logic.

3. Security

Stored procedures provide an additional layer of security. By using stored procedures, users can be granted permission to execute a procedure without having direct access to the underlying tables. This can help prevent SQL injection attacks and limit access to sensitive data.

4. Consistency and Maintainability

By centralizing the logic in the database, stored procedures ensure that the same business rules are applied consistently across all applications. This makes maintenance easier because any changes to the logic need to be made only once in the procedure rather than in every application that uses it.

5. Atomicity

Stored procedures are executed as a single unit of work. If there’s an error during execution, MySQL can handle transactions within the procedure, ensuring that all operations are completed or none at all, preserving the consistency of the data.

Cons of Using Stored Procedures in MySQL

1. Debugging Complexity

Stored procedures can be harder to debug compared to regular SQL queries, especially when dealing with large or complex procedures. Error handling can also be tricky, requiring additional effort to catch and log issues.

2. Limited to MySQL

Stored procedures written in MySQL are specific to the MySQL server and might not be easily portable to other databases. If you plan on switching to a different database management system, stored procedures may need to be rewritten.

3. Performance Overhead

While stored procedures can improve performance by reducing network traffic, the execution of complex stored procedures can sometimes introduce overhead on the database server, especially if the procedure performs heavy computations or handles large data sets.

4. Maintenance Overhead

As business logic grows, stored procedures can become a maintenance burden. Large numbers of stored procedures can make the database more complex, especially if many procedures depend on each other.

5. Lack of Flexibility

Stored procedures are static, which means changing the logic often requires modifying the procedure itself. Unlike application code that can easily be changed and deployed, modifying stored procedures typically requires altering the database schema and might involve downtime.

Trade-offs

1. Complexity vs. Performance

Stored procedures can significantly improve performance by reducing the number of queries sent from the application to the database. However, they introduce additional complexity, especially when debugging and maintaining the logic.

2. Scalability

Stored procedures can become a bottleneck if the database is under heavy load, as they run on the database server. For large-scale applications, it may be worth considering other performance optimizations, such as caching or offloading heavy computation to the application layer.

3. Maintainability

As your system evolves, the stored procedure approach may become harder to manage. Over time, you may find that a mix of application logic and stored procedures works better, with critical business logic stored in the database for performance, while less critical logic is handled at the application level.

Conclusion

Stored procedures in MySQL offer many benefits, from improving performance and security to promoting code reusability and consistency. However, they also come with trade-offs, such as increased complexity, potential performance overhead, and challenges with portability and debugging. As with any tool, it’s important to evaluate the specific needs of your application and determine if stored procedures are the right choice.

Appendix

Blog: How a SQL statement is executed.