Summary

In this chapter, we have examined the different types of UDFs and looked at creating reliable functions. We examined both deterministic and non-deterministic functions and discussed the requirements for a function to be deterministic.

We then looked at calling UDFs and scalar valued functions. Our discussions also included the Table data type and the advantages and pitfalls in using it. We also looked at the SQL Server's in-built functions that return Table data types.

We then discussed schema bindings and finally went on to examine the similarities between stored procedures and UDFs. UDFs share a number of similarities with stored procedures, but as we saw there are a number of restrictions too. None is more restrictive than the inability to modify data in existing tables; however, data modification isn't what a UDF is about. UDFs are there to provide us with a value or a set of data based on a set of criteria.