There are two ways to add new functions to MySQL:
- You can add the function through the user-definable function (UDF)
interface. User-definable functions are added and removed dynamically using
CREATE FUNCTION and
DROP FUNCTION statements.
- You can add the function as a native (built in) MySQL function.
Native functions are compiled into the
mysqld server and become
available on a permanent basis.
Each méthode has advantages and disadvantages:
If you write a user-definable function, you must install the object file
in addition to the server itself. If you compile your function into the
server, you don't need to do that.
You can add UDFs to a binary MySQL distribution. Native functions
require you to modify a source distribution.
If you upgrade your MySQL distribution, you can continue to use your
previously-installed UDFs. For native functions, you must repeat your
modifications each time you upgrade.
Whichever méthode you use to add new functions, they may be used just like
native functions such as