[thelist] "A Brief Rhapsody on Art and Engineering"
Rudy_Limeback at maritimelife.ca
Rudy_Limeback at maritimelife.ca
Fri Sep 8 12:52:55 CDT 2000
>> http://www.microship.com/index.html
>
> Thanks for sending this; absolutely wonderful
yes, thanks steve
and yes, there's some really good content
but this microship guy is a total fruitcake, i've seen tv and magazine
articles about his bike trips
so is pirsig, the author of zen and the art of motorcycle maintenance,
which i liked so much (who didn't?) that i read the followup lila, a total
disappointment
and of course, i mean "total fruitcake" in a fond and friendly way
i have nothing but admiration for people living on the edge of sanity (or,
as in pirsig's case, on the other side of it), for they are blessed with
true creativity, and often an unrelenting drive to get things done...
<tip type="sql"
synopsis="GROUP BY and ORDER BY are not the same">
ORDER BY returns results in the requested order --
/* list categorys by name */
select category
from categorys
order by category
ORDER BY returns detail rows, i.e. one row for each row in the results
table
GROUP BY, on the other hand, returns summary rows --
/* count articles by category */
select category,count(*)
from categorys, content
where categorys.categoryid = content.categoryid
group by category
GROUP BY returns one row for each *group* in the results table
usually GROUP BY without ORDER BY will (as expected) return results in
GROUP BY order, but this is not actually guaranteed
if you *have* to have results in GROUP BY order, include the ORDER BY --
/* list categorys with article count */
select category,count(*)
from categorys, content
where categorys.categoryid = content.categoryid
group by category
order by category
of course, you can also have a different sequence --
/* list categorys by most articles */
select category,count(*)
from categorys, content
where categorys.categoryid = content.categoryid
group by category
order by 2 desc
</tip>
two for the price of one --
<tip type="sql"
comment="very important for web-database response time">
take a long, hard look at database calls inside a loop, and find a way to
eliminate the loop -- table joins can solve most of these situations
</tip>
rudy
r937.com
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