What is the difference between a stored procedure and a function?

A function must return a value or table and is designed to participate in SQL expressions or relational queries, subject to SQL Server's function restrictions. A stored procedure is invoked as an executable module and can perform a much wider range of operations.

Stored procedures can return multiple result sets, use output parameters, execute dynamic SQL, and perform data modifications. Functions are more constrained and should not be treated as replacements for procedures.

The appropriate choice depends on whether the logic needs to compose inside a query or execute as an independent database operation.