What are stored procedures in relational databases?

Stored procedures are predefined blocks of SQL code stored within a relational database that perform specific operations when called. They are similar to functions in programming languages, allowing developers to encapsulate complex database logic into reusable units. Stored procedures accept input parameters, execute queries, perform calculations, and return results. For example, a stored procedure might handle inserting a new order into a sales database, updating inventory, and calculating discounts in a single call. By centralizing this logic on the database server, stored procedures reduce code duplication and ensure consistent execution of business rules.

One key advantage of stored procedures is performance optimization. Since the code is precompiled and stored on the database server, execution is often faster than sending raw SQL statements from an application, especially for complex operations. They also minimize network traffic—instead of sending multiple queries, an application calls a single procedure. Additionally, stored procedures enhance security by limiting direct access to tables. For instance, a procedure could validate user permissions before modifying sensitive data, reducing the risk of SQL injection attacks. Transactions can also be managed within procedures, ensuring all steps either succeed or fail together, which maintains data integrity.

However, stored procedures have trade-offs. Overusing them can lead to logic being split between the application and database layers, complicating maintenance. Vendor-specific syntax (e.g., differences between PostgreSQL and SQL Server) can also create migration challenges. They’re best suited for performance-critical operations, data validation, or tasks requiring atomic transactions. For example, a banking system might use a stored procedure to transfer funds between accounts, ensuring balance checks, debits, and credits occur as a single unit. When designed thoughtfully, stored procedures are a powerful tool for streamlining database interactions while enforcing consistency and efficiency.