Description: A stored function is a type of stored procedure that returns a value. It is a set of SQL instructions stored in the database, which can be invoked to perform specific operations. Stored functions allow encapsulating business logic, facilitating code reuse, and simplifying complex queries. Unlike stored procedures, which can perform data modification operations, stored functions are primarily designed to return a value and can be used in SQL expressions, making them very versatile. Additionally, being precompiled, they can improve query performance, as the database engine can optimize their execution. Stored functions are especially useful in environments where consistency and efficiency in data access are required, allowing developers and database administrators to implement more effective and maintainable solutions.
History: Stored functions emerged in the 1970s with the development of relational database management systems. As databases evolved, the need to encapsulate business logic and complex operations into reusable procedures became evident. In 1986, the SQL-86 standard introduced the concept of stored procedures, which later expanded to include stored functions in later versions of the SQL standard. Over time, different database management systems, such as Oracle, SQL Server, and PostgreSQL, have implemented their own versions of stored functions, each with specific features and syntax.
Uses: Stored functions are primarily used to encapsulate business logic that can be reused across multiple queries. They are useful for performing complex calculations, validating data, and transforming information before it is presented. They are also employed to enhance security, as they allow restricting direct access to tables and exposing only the necessary functions. In development environments, they facilitate collaboration among teams, as developers can work on specific functions without affecting the rest of the system.
Examples: A practical example of a stored function could be one that calculates sales tax based on a product’s price. This function could be called in a query to obtain the total price including tax. Another example would be a function that validates whether a customer ID exists in the database, returning a boolean value indicating its existence.
