ABAP_to_the_Future

Top-Down Development 15.2
USING zt_monsters zt_monster_items.
" SQLScript code goes here
ENDMETHOD.
ENDCLASS.
Listing 15.12 Implementing a Method so that It Runs inside the Database
After the method implementation in Listing 15.12, you’ll see the words BY DATA-
BASE PROCEDURE, which says that this method will generate and execute a stored
procedure in the database at runtime. Having the control in the implementation
as opposed to the definition is a stroke of genius: It means you can redefine the
method so that subclasses can run the method in the server or in the database, or
during unit tests a test double can just return hard-coded values. In addition to
the obvious benefit for unit testing, if you’re dubious as to whether pushing a certain
method down to the database is re ally worthwhile, then you can create one
class that runs in the server and a subclass that runs in the database and do some
tests where you swap between them to compare the runtime.
The next line in Listing 15.12 says FOR hdb, which means that you want to use an
SAP HANA database, and LANGUAGE, to say what language you want. As Henry
Ford once said, “You can have any color you want, as long as it is black.” In the
same way, you have these options to specify what database you can use (it has to
be SAP HANA) and what language you are going to code the AMDP in (it has to
be SQLScript).
Finally, in Listing 15.12 you have the USING statement, in which you have to give
an explicit list of what database tables (or views) you’re going to use within the
procedure. It’s also possible for one database procedure to call another, and if you
want such a thing, then you have to mention the database procedure you’re going
to invoke in this list as well. This whol e concept will seem strange to ABAP programmers,
who are used to just reading from whatever database table takes their
fancy and calling global functions and methods at will, but remember: You’re in
another world now, the world of the database, where the laws of physics are different,
and water flows uphill; this is programming, but not as you know it.
Restrictions
You cannot create the AMDP coding (or any sort of SAP HANA artifact, for that matter)
in SE24 or SE80. You can display it, but to create or change the code you need to use
ABAP in Eclipse. (Hopefully Chapter 1 convin ced you that is the best tool to use any-
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