--- In firebird-support@yahoogroups.com, Helen Borrie <helebor@t...>
wrote:

> At 11:05 PM 6/06/2004 +0000, you wrote:
> >I just looked into rfunc2 source code, and they seem to use the
> >following idiom:
> >
> > select func(...) from RDB$DATABASE;
> >
> >I guess I missed this in the docs.
> >
> >I still think 'execute function' support would be nice syntactical
> >sugar.
>
> Hmm, a function is a function, not a procedure! It's just like

any SQL

> function: designed to take constants as inputs and return a

result.

> Functions operate on values, procedures operate on objects.
>
> Actually, you can sometimes satisfy a need for a function by

writing a

> stored procedure: that is, it is not a requirement for a

procedure to

> query the database. The reverse is not true: you must never

write a

> function that has to query the database.
>
> Things are getting more blurred these days: RDBMS engines, esp.

the

> object-relational ones, are acquiring the ability to let you

define

> internal objects with their own functionality using a specialised

JVM

> that's part of the engine. There's been discussion from time to

time in

> firebird-architect about doing something like this with Firebird,

via a

> plug-in - so don't give up hope!

Hmm; sorry, the distinction between stored procs and UDF's is still
a bit fuzzy in some ways. I understand from reading the InterBase
docs that UDF's should be very short, simple functions so they won't
tie up the database, esp. in the multi-threaded server (and, as you
said, they shouldn't query the database - and they certainly
shouldn't modify it as that may leave the database in an
inconsistent state. IIRC).

So, that's pretty distinctive. ;-)

But is there anything wrong with creating a simple UDF that returns
a value, like this:

isql> select generate_guid_udf();

Rather than having this weird syntax (I guess that's where I'm
confused - why is this necessary? Is this even the proper idiom? I
just grabbed it and started using it because it worked)

isql> select generate_guid_udf() from RDB$DATABASE;

thnaks!
--craig