What is difference between function and stored procedure in sql server?

A stored procedure is like a miniture program in SQL Server. It can be as simple as a select statement, or as complex as a long script that adds, deletes, updates, and/or reads data from multiple tables in a database. (Stored procedures can also implement loops and cursors which both allow you to work with smaller results or row by row operations on data.) The SQL Server functions are option for doing certain operations in SQL Server. They can not be used to update, delete, or add records to the database. They simply return a single value or a table value. They can only be use to select records. However, they can be called very easily from within standard SQL, such as: SELECT dbo.functionname('Parameter1') OR SELECT Name, dbo.Functionname('Parameter1') FROM sysObjects For simple reusable select operations, functions can simply your code. Just be wary of using JOIN clauses in your functions. If your function has a JOIN clause and you call it from another select statement that returns multiple results, that function call with JOIN those tables together for EACH line returned in the result set. So though they can be helpful in simpling some logic, they can also be a performance bottleneck if they're not used properly.