Functions and Triggers

So far in this chapter, we have discovered how to quantify query performance via the query planner, as well as the benefits of using joins to collate and extract information from multiple database tables. In this section, we will construct reusable queries and statements via functions, as well as automatic function execution via trigger callbacks. The combination of these two SQL features can be used to not only run queries or re-index tables as data is added to/updated in/removed from the database, but also to run hypothesis tests and track their results throughout the life of the database.

Function Definitions

As in almost all other programming or scripting languages, functions in SQL are contained sections of code, which provides a lot of benefits, such as efficient code reuse and simplified troubleshooting processes. We can use functions to repeat/modify statements or queries without re-entering the statement each time or searching for its use throughout...