Procedures vs. Functions in SQL

This post explains the differences between Procedures and Functions

5/21/20233 min read

In SQL, procedures and functions are essential constructs for creating reusable and modular code. While they share similarities, they have distinct characteristics and serve different purposes. This article aims to provide a comprehensive understanding of the differences between procedures and functions in SQL. We will explore their definitions, usage scenarios, return values, parameter passing, and transaction control.

  1. A procedure is a named collection of SQL statements that perform a specific task or set of tasks. It is designed to carry out a sequence of actions, such as data manipulation, data retrieval, or business logic implementation. Procedures can be invoked by other SQL statements or called explicitly.

On the other hand, a function is also a named set of SQL statements, but it is designed to return a single value or a table. Functions are used to encapsulate and execute a specific computation or operation, which can be used in SQL expressions or as a part of queries.

  1. Return Values: One of the key differences between procedures and functions is their return behavior.

    A procedure does not necessarily return a value explicitly. Its primary purpose is to perform actions or modify data within the database. However, procedures can utilize output parameters to return values, which can be useful for passing back results or status information to the calling program.

    On the other hand, a function must return a value explicitly. The return type is defined during the function's creation, and it must be specified in the function definition. Functions can return scalar values (e.g., integers, strings, booleans) or result sets (e.g., tables).

  2. Parameter Passing: Both procedures and functions can accept input parameters, but there are differences in how they handle parameter passing.

    In procedures, parameters can be of three types: IN, OUT, or INOUT. IN parameters are used for passing values into the procedure, OUT parameters are used for returning values from the procedure, and INOUT parameters can be used for both input and output purposes. Procedures can have zero or more parameters, allowing flexibility in passing values and retrieving results.

    Functions also accept input parameters, which are used to perform computations or operations. However, functions cannot have OUT or INOUT parameters. Functions are designed to return a value, and the parameters are used as input to generate the result.

  3. Usage Scenarios : Procedures and functions have different usage scenarios based on their characteristics and intended purposes.

    Procedures are typically used for:

    • Performing data manipulation operations, such as inserting, updating, or deleting records.

    • Executing complex business logic or calculations.

    • Controlling flow and implementing control structures.

    • Grouping a set of SQL statements to be executed as a single unit.

    Functions, on the other hand, are commonly used for:

    • Calculations and computations, such as mathematical operations or string manipulations.

    • Returning values that are used in SQL expressions or queries.

    • Encapsulating frequently used logic for code reusability.

    • Enhancing the readability and maintainability of SQL code.

    1. Transaction Control (approx. 200 words):Transaction control is another area where procedures and functions differ.

    Procedures can include transaction control statements, such as COMMIT and ROLLBACK, allowing the developer to manage transaction boundaries explicitly. This enables procedures to initiate or terminate transactions as required.

    Functions, however, have limitations when it comes to transaction control. They cannot contain explicit transaction control statements since they are not intended to modify data directly. Functions are considered to be part of a transaction context defined by the calling code.

    Conclusion :Procedures and functions in SQL serve distinct purposes and have unique characteristics. Procedures are used for executing a sequence of actions or implementing complex business logic, while functions are designed to return values or result sets for calculations and computations. Understanding the differences between procedures and functions is crucial for choosing the appropriate construct based on the requirements of the SQL code. By leveraging the strengths of each construct, developers can create modular, reusable, and efficient SQL code.