The Difference Between Stored Procedure and User-Defined Function in T-SQL

When it comes to T-SQL, understanding the difference between a stored procedure and a user-defined function is essential for efficient database management and query optimization.

Stored Procedure

A stored procedure is a predefined SQL query that is stored in the database server for future use. It allows you to execute a set of SQL statements by calling the procedure name. Stored procedures can accept input parameters and return multiple result sets, making them versatile for complex data manipulation tasks.

User-Defined Function

On the other hand, a user-defined function is a reusable code block that accepts input parameters and returns a single value. Functions are used to perform specific operations and computations within SQL queries. Unlike stored procedures, user-defined functions cannot perform data manipulation operations or transactions.

Key Differences

• Usage: Stored procedures are used for executing a series of SQL statements, while user-defined functions are used to return a single value.
• Data Manipulation: Stored procedures can manipulate data and perform transactions, whereas user-defined functions are restricted from modifying data.
• Performance: Stored procedures are faster than user-defined functions due to their ability to cache query plans, leading to improved performance in repetitive tasks.

In conclusion, understanding when to use a stored procedure versus a user-defined function is crucial for optimizing T-SQL queries and enhancing database performance.