As far as I can see ALIAS is used to assign long column names to fields.
RENAME TABLE can be used to assign long table names
Not to take up a recent discussion (on linkedin), but DDS has some
advantages over DDL and the most important are
a. DDS support EDTCDE and EDTWRD, DDL doesn't
b. DDS support CHGPF making Change Management simple, DDL doesn't
c. DDS support Referential Information stored prior to V7R1, DDL requires
V7R1 or later
As Nathan writes the DB objects created is more or less identical so there
is nothing that prevents creating DB objects with DDS and afterward alters
them with DDL.
Besides that there are tons of DDS out there and converting these to DDL is
not only a waste of time but may also interfere with existing Change
Management systems.
I have looked into making a Data Definition/Change Management system based
on DDL and that is far more complicated than initial meets the eye because
the structure of SQL where columns and its properties can't be defined in a
single statement and SQL doesn't have the automatization level that
DDS/CHGPF (that implement all changes to a DB object in one command) has.
In fact if we want to make a Data Definition system with build in Change
Management we will need some kind of markup language similar to DDS
(probably XML) where we automatically can generate the DDL’s needed for
changes made to different versions of the DB otherwise we will code
ourselves to death.
And here comes the funny thing, guess what DDS/CHGPF runs under the hood?
DB2 UDB SQL Basic Services (QSYS/QSQSBAS)! So why reinvent the wheel?
Many things are hidden on IBM I. Query runs SQL under the hood, ILE program
compilers doesn’t generate MI code but an intermediate W-code that compiles
to the MI version of the OS when we either compile or install an object or
JIT compiles it after installation (that’s why we can move objects between
releases) and so forth. Java has the same facility. It comes compiled as
java bytecode and is translated into specific MI by the JVM. PASE (that
also runs the JVM) is actually a AIX/UNIX Virtual Machine that is why
platforms like Node.JS that first was ported from Linux to AIX also runs on
IBM I with very little effort.
Many regards SQL/DDL as a new kid in town but it is actual first described
in 1970 and became an ANSI standard in 1986 and an ISO standard in 1987
where DDS origins from 1979 and even if it IBM proprietary it is still
widely used to describe DB, DSPF, PRTF, RPGOA interfaces etc. so as long as
we are on IBM I and codes in ILE RPG/COBOL there is no way we can throw the
baby out with the bathwater.
An intermediate approach could be – combine it!
On Wed, Oct 22, 2014 at 1:02 AM, Nathan Andelin <nandelin@xxxxxxxxx> wrote:
Nice tip, Vern ... use RENAME TABLE after the file exists.
The fact that it works shouldn't be a surprise to me, I have used ALTER
TABLE to add and remove columns from tables created via DDS.
I suppose the notion of DDS being mutually exclusive from DDL and visa
versa is materially flawed. The actual database objects (files) are
identical in most respects.
Nathan.
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