Using UDFs to avoid cursors

Let's say you have 2 tables: a Contacts table and a PhoneNumbers table (which stores all the phone numbers for each contact).  You are asked to write a query that returns each contact's name and a comma-delimited string of phone numbers for each contact, something like this:

FirstName    LastName   PhoneNumbers
---------    --------   --------------------------
John         Smith      111-222-3333, 444-555-6666

Many developers would attempt to do this with a cursor.  While a cursor could certainly be coded to do the job, there is actually a more efficient way of doing this that doesn't require cursors or temp tables.

You would write a UDF that grabs the phone numbers, and then execute the UDF within a SELECT statement, as the following code demonstrates: