What is the purpose of stored procedures in SQL?

Stored procedures in SQL serve to encapsulate and centralize database logic. They are predefined SQL scripts stored in the database that perform specific tasks, such as querying data, updating records, or executing complex transactions. By bundling SQL statements into reusable modules, stored procedures reduce code duplication and ensure consistent implementation of business rules. For example, a procedure might handle inserting a new order into a sales database: it could validate inputs, update inventory, and calculate taxes in a single call. This modularity simplifies application code, as developers can invoke the procedure instead of embedding the same logic across multiple application layers.

A key benefit of stored procedures is improved performance. When a procedure is created, the database engine often optimizes and caches its execution plan, reducing the overhead of parsing and planning SQL statements each time they run. This is especially useful for complex operations, like generating reports that join multiple tables or aggregate large datasets. Additionally, stored procedures minimize network traffic. Instead of sending individual SQL commands from an application to the database, a single procedure call executes all required steps on the server. For instance, a banking application could use a stored procedure to transfer funds between accounts, executing both the withdrawal and deposit in one server-side operation, which reduces latency and round trips.

Stored procedures also enhance security and maintainability. By granting users permission to execute procedures instead of direct access to tables, administrators can enforce data integrity and limit exposure to sensitive information. For example, a procedure might restrict which columns a user can modify in a customer table. Maintenance becomes easier because changes to the procedure’s logic—like fixing a bug or adding a new validation rule—are applied once in the database, eliminating the need to redeploy application code. This centralized approach reduces errors and ensures all applications using the procedure adhere to the updated behavior.