Re: function to operate on same fields, different records?

On Thu, Mar 29, 2001 at 06:05:04PM -0800, Eric G. Miller wrote:
> On Thu, Mar 29, 2001 at 01:17:29PM -0600, will trillich wrote:
> > is this kind of thing possible---?
> > 
> > 	select gpa(student) from student where id=7121;
> > 	select gpa(course) from course where id=29931;
> > 	select gpa(prof) from prof where id=1321;
> 
> SELECT sum(grade) / count(grade) As GPA FROM grades;
>                     ^^^^ (bad juju if 0)
> Where grades is;
> 
> create table grades (
> 	exam	int4,
> 	who	int4,
> 	grade	real,
> 	PRIMARY KEY (exam, who),
> 	FOREIGN KEY (who) REFERENCES student (student_id)
> );
> 
> I'm not sure why you have a separate column for each grade... Probably
> missing something...

also want to keep statistics on /how many/ F's, A's, etc.
one F, one A give the same GPA as two C's.

	select * from course where a > 2 * f ;

but back to the original question --

even using PLPGSQL, is it possible to send VARYING relation
tuples to a procedure/function -- so long as the attributes
(fields) munged within the function are common to all tables?

	create function gpa ( opaque ) returns float8 as '
	declare
		rec alias for $1;
	begin
		return (rec.D + (2*rec.C) + (3*rec.B) + (4*rec.A))
			/  (rec.F + rec.D + rec.C + rec.B + rec.A);
	end;' language 'plpgsql';

here, REC could be

	create table course (
		topic varchar(6),
		num   int4,
		name  varchar(80),
		a     int4,
		b     int4,
		c     int4,
		d     int4,
		f     int4
	);
or
	create table student (
		id    serial,
		name  varchar(80),
		a     int4,
		b     int4,
		c     int4,
		d     int4,
		f     int4
	);
or
	create table prof (
		id    serial,
		name  varchar(80),
		office varchar(40),
		phone  varchar(10),
		a     int4,
		b     int4,
		c     int4,
		d     int4,
		f     int4
	);

i'm hoping the same function could handle any of those different
tuple types so long as the attributes (fields) accessed are
common to all of them. impossible?

-- 
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will@serensoft.com
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