Hi!
...From: Tom Crimmins <[EMAIL PROTECTED]> To: sguazt sguazt <[EMAIL PROTECTED]> CC: mysql@lists.mysql.com Subject: RE: Queries inside UDF Date: Wed, 16 Mar 2005 10:09:16 -0600
Can you explain exactly what you are using this for? What benefit does this provide over just executing the query?
You can either execute SELECT foobar() or SELECT COUNT(*) FROM tblfoobar,
and
you don't have to do anything to make the latter work. Creating the UDF just
seems like a lot of extra work. Maybe this is my ignorance, but I don't see
much use for executing a query within a UDF esspecially if you are using 4.1
with subqueries.
ok sorry if I submitted a stupid exampe :P but I wanted to keep the stuff simple. My real case is a little more complicated ...
First of all, unfornately I've to use MySQL 4.0.21.
The purpose of creating a UDF, in my case, is doing something that in my opinion cannot be done in a query.
For example, if you have to implement in SQL the following pseudo-code:
start = <a unix timestamp>; duration = 100; stop = null; increment = 0;
while ( true ) {
start2 = 0;
stop2 = 0;stop = start + ( duration - increment );
rs = doQuery( "SELECT start,stop FROM t1 INNER JOIN t2 ON t1.c1=t2.c1 .... WHERE t1.start>=" + start + " AND t1.stop<=" + stop );
if ( rs == null ) {
delta = 0;
start2 = rs[0]['start']; stop2 = rs[0]['stop'];
if ( start < start2 ) {
delta += start2 - start;
}
increment += delta;
start = stop2
}
else {
break;
}
}
return stop;what do you write?
The main problem is that you can establish a-priori when you stop the main while ... :(
I thought to use a temporary table but the problem remains ...
Furthermore that code produces an info that is to be used by another (more complex) query.
So the only solutions are:
1. use a high-level language (C,perl,Java,PHP) and implement the entire logic (not only the code above) in that language (but this seems to be too slow ... I did it before exploring the UDF world ;) )
2. try to write a UDF that implement the code above; so you create a UDF, e.g. named foobar, you can use inside other query: SELECT ...,foobar( start, duration ) AS stop FROM <a very long JOIN> ...
Any idea?
bye!!!
-- Marco
-- Tom Crimmins Interface Specialist Pottawattamie County, Iowa
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