Some good examples of how to deal with this in PHP have already been
given, especially the associative array solution.
The question I have is with something like this, how do you weight out
the pros/cons of code development versus speed?
i.e. for code development breaking the logic up into 2 queries would
yield a much more readable result, but speed wise what is better
multiple queries with smaller more precise record sets, or having PHP
parse through the result set to properly weed out duplicate titles based
on the outer join applied?
This is assuming that there is no SQL construct to solve this problem,
which personally I know of none.
-Brad
Andrew Darby wrote:
Hello, all. I don't know if this is a php-mysql question or just a
mysql, but here goes:
I have a list of DVDs that my library loans out, and I'd like to allow
people to add comments to each item. Since this list gets regenerated
periodically (it's extracted from another system, the library
catalog), there isn't a consistent ID in the dvd tables, so I'm using
the call number (which will look like DVD 2324) as the key. Anyhow, I
join the tables like this to get all the DVDs and all the comments
associated with the DVDs:
SELECT distinct dvds.title, dvds.publisher, dvds.publication_date,
dvds.call_number,
comment.id, comment.parent_id, comment.comment, comment.name
FROM dvds
LEFT JOIN comment
ON dvds.call_number=comment.parent_id
WHERE dvds.title LIKE 'A%'
ORDER BY dvds.title
With this, I'll get results like
DVD 101 A.I. This movie rocked
DVD 101 A.I. This Movie stunk
DVD 102 Adaptation . . .
DVD 103 After Hours . . .
When I loop in PHP through the records, of course, I want just the one
DVD with however many comments associated with it. Is it possible to
do this (i.e., screen out DVD dupes) in MySQL, or do I have to do it
in PHP?
If this is a dumb question, my humblest apologies, and I'd be
interested if there was a better way to handle this . . . .
Andrew
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