This chapter is about teaching SQLite new tricks. The previous chapter dealt with generic database work; this chapter is about being creative. The latter half of the API—the Extension API—offers three basic ways to extend (or customize) SQLite, through the creation of user-defined functions, aggregates, and collation sequences.
User-defined functions are SQL functions that map to some implementation that you write. They are callable from within SQL. For example, you could create a function
hello_newman() that returns the string
'Hello Jerry' and, once it is registered, call it from SQL as follows:
sqlite > select hello_newman() as reply; reply ------------------ 'Hello Jerry'
This is a special version of the SQLite ...