How does a UDF differ from a stored procedure?

How does a UDF differ from a stored procedure?

• A. A UDF must return a value and can be used inline, while a stored procedure may not.
• B. A UDF can modify data freely.
• C. A UDF generally cannot modify data, and is used in SQL expressions.
• D. A UDF cannot be used in SQL expressions.

Answer: (C)

A user-defined function is meant to be used inside a SQL statement, returning a value that you can compute or filter on. Because it’s intended to be a pure computation that blends into expressions, it generally cannot modify data in the database. This is why you can place it in a SELECT list, in a WHERE clause, or in a computed column, treating it like a built‑in function. Stored procedures, on the other hand, are designed to perform actions. They’re invoked with a separate call and can run logic that changes data, calls other procedures, or return multiple result sets and output parameters. They aren’t meant to be embedded inside SQL expressions. So the best way to summarize the distinction is that a UDF is used inline in SQL expressions and is expected to return a value without side effects on data, whereas a stored procedure is an operation you execute to perform tasks, including data modification.

A user-defined function is meant to be used inside a SQL statement, returning a value that you can compute or filter on. Because it’s intended to be a pure computation that blends into expressions, it generally cannot modify data in the database. This is why you can place it in a SELECT list, in a WHERE clause, or in a computed column, treating it like a built‑in function.

Stored procedures, on the other hand, are designed to perform actions. They’re invoked with a separate call and can run logic that changes data, calls other procedures, or return multiple result sets and output parameters. They aren’t meant to be embedded inside SQL expressions.

So the best way to summarize the distinction is that a UDF is used inline in SQL expressions and is expected to return a value without side effects on data, whereas a stored procedure is an operation you execute to perform tasks, including data modification.