288 Chapter 14: Writing and Executing SQL Routines and Modulesx Note: Support for SQL programming varies considerably from one DBMS to another. This chapter presents what is documented in the SQL standard, but it is highly likely that what is available with your DBMS will be different from what you see here, at least to some degree. You should therefore use what is in this chapter as a starting point for your DBMS's SQL programming support and verify the specifics with your software's documentation. SQL Programming Elements The smallest unit of a SQL PSM is a routine. Typically a rou- tine will perform a single action, such as updating a total or inserting a row in a table. Routines are then gathered into modules. There are three types of routines: Procedures: Procedures are executed with the SQL CALL statement. They do not return a value. Functions: Functions return a typed value and are used