[PHP-DB] MySQL/PHP Left Join Question
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 101A.I. This movie rocked DVD 101A.I. This Movie stunk DVD 102Adaptation . . . DVD 103After 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 -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DB] MySQL/PHP Left Join Question
One thing I've done in situations like this is just load your returned DB data
into an array. Something like this would do:
$dvdarr[$result['call_number']]['Title'] = $result['title'];
$dvdarr[$result['call_number']]['Publisher'] = $result['publisher'];
$dvdarr[$result['call_number']]['Comments'][] = $result['comment'];
Put that in a loop of your results. Notice the [] on the comments. That'll
collect all your comments under the umbrella of 'Comments'.
Then when you go to do your output, you'd do something like this:
forach ($dvdarr as $callnumber = $dvddata) {
$title = $dvddata['Title'];
$publisher = $dvddata['Publisher'];
$comments = $dvddata['Comments'];
foreach ($comments as $comment) {
// do whatever
}
}
There are other ways to handle this.. this might be one of the easier ones (if
I'm understanding your problem correctly).
-TG
= = = Original message = = =
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 101A.I. This movie rocked
DVD 101A.I. This Movie stunk
DVD 102Adaptation . . .
DVD 103After 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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RE: [PHP-DB] MySQL/PHP Left Join Question
I approach this by assigning a value to a variable and then comparing to see
if i need to write out a new title
$oldDVD = ;
while ($rows=mysql_fetch_array($result))
{
//decide whether to show the DVD title
if ($oldDVD != $rows['title'])
{
echo trtd.$rows['title']./td/tr;
$oldDVD = $rows['title'];
}
//echo out the rest of the data
echo trtd.$rows['comment']./td/tr;
}
hth
Bastien
From: Andrew Darby [EMAIL PROTECTED]
To: php-db@lists.php.net
Subject: [PHP-DB] MySQL/PHP Left Join Question
Date: Thu, 25 May 2006 11:28:56 -0400
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 101A.I. This movie rocked
DVD 101A.I. This Movie stunk
DVD 102Adaptation . . .
DVD 103After 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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Re: [PHP-DB] MySQL/PHP Left Join Question
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 101A.I. This movie rocked DVD 101A.I. This Movie stunk DVD 102Adaptation . . . DVD 103After 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 -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DB] MySQL/PHP Left Join Question
Thanks to Bastien and TG for their suggestions. I'd been looking at it Bastien's way, but TG's is probably better suited to what I want to do. I'd forgotten about that possibility, cramming it all into an array . . . . Again, thanks for the help, Andrew p.s. I'd be curious about the relative speeds of these methods, too. -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DB] MySQL/PHP Left Join Question
test both and let us know bastien From: Andrew Darby [EMAIL PROTECTED] To: php-db@lists.php.net Subject: Re: [PHP-DB] MySQL/PHP Left Join Question Date: Thu, 25 May 2006 12:33:15 -0400 Thanks to Bastien and TG for their suggestions. I'd been looking at it Bastien's way, but TG's is probably better suited to what I want to do. I'd forgotten about that possibility, cramming it all into an array . . . . Again, thanks for the help, Andrew p.s. I'd be curious about the relative speeds of these methods, too. -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
