Combining mySQL tables into one row? - php

Question

I have four tables that are linked.
images Table
cid link
=======================
1 something.jpg
2 else.jpg
terms Table
cid term is_attr
================================
1 Location 0
2 Caption 1
3 Camera Lens 0
tags Table
cid Name term_id
==============================
1 somewhere 1
2 BFE 1
3 A word 2
linked_tags Table
cid photo_id tag_id
==========================
1 1 1
2 1 2
3 1 3
if a Term is_attr == 1 the image should only have ONE entry in the linked_tags table for that term.
If I were to query the image table and get the tags at the same time, how would I do that?
I'd like to have (something) this returned:
_____________________________________________________________________________
cid |link |attributes |tags |
=========|==================|==================|====================|
1 |something.jpg |__________________|____________________|
| ||term |value |||term |value ||
| ||========|=======|||========|=========||
| ||caption |A word |||Location|somewhere||
| || | |||Location|BFE ||
This is what I am looking for (PHP side):
//Row 1
array(
'link' => "something.jpg",
'attributes' => array('caption'=>"A word"),
'tags' => array('Location'=>array('somewhere','BFE'))
);
//Notice 'caption' points to a string and 'location' points to an array
//Row 2
array(
'link' => "else.jpg",
'attributes' => array(),
'tags' => array()
);
// OR
array(
'link' => "else.jpg"
);
// OR
array(
'link' => "else.jpg",
'attributes' => array('caption'=>""),
'tags' => array();
);

Answer 1

SELECT i.*, GROUP_CONCAT(tag.name SEPARATOR ', ')
FROM image i
JOIN tag
ON tag.image_id = i.id
GROUP BY
i.id
Update:
Tabular format assumes same number of columns in each record, all having the same type across the records.
Your task is best done in three queries:
SELECT cid, link
FROM image
WHERE cid = 1
(cid and link)
SELECT t.name, tag.name
FROM linked_tags lt
JOIN tags
ON tags.cid = lt.tag_id
JOIN terms t
ON t.cid = tags.term_id
WHERE lt.photo_id = 1
AND t.is_attr = 1
(attributes)
SELECT t.name, tag.name
FROM linked_tags lt
JOIN tags
ON tags.cid = lt.tag_id
JOIN terms t
ON t.cid = tags.term_id
WHERE lt.photo_id = 1
AND t.is_attr = 0
(tags)

Answer 2

Most likely you'd want to the GROUP_CONCAT function.
edit:
phooey. Quassnoi beat me to the punch. Just as a warning: GROUP_CONCAT's output is length limited (usually 1024 bytes by default), but you can override it with the group_concat_max_length run-time setting.

Answer 3

Am I missing something, or does this just need a few LEFT JOINs?
$query = 'SELECT images.cid, images.link, terms.term, tags.name, terms.is_attr FROM images LEFT JOIN linked_tags ON images.cid = linked_tags.photo_id LEFT JOIN tags ON linked_tags.tag_id = tags.cid LEFT JOIN terms ON tags.term_id = terms.cid WHERE 1 ORDER BY images.cid';
$result = mysql_query($query);
The result set will give you multiple rows for each image, and you can use PHP to parse the data into whatever format you need like this.
$image_list = array();
while ($line = mysql_fetch_assoc($result)) { // fetch mysql rows until there are no more
if (!isset($image_list[$line['cid']]) { // checks to see if we have created this image array row yet
// if not, create new image in image array using cid as the key
$image_list[$line['cid']] = array('link' => $line['link'], 'attributes' => array(), 'tags' => array());
}
if ($line['term'] != null) { // if there are no linked attributes or tags, move on to the next image leaving both arrays empty, otherwise...
if ($line['is_attr']) {
// if attribute row, add attribute using term as key
$image_list[$line['cid']]['attributes'][$line['term']] = $line['name'];
} else {
// if tag row, add tag using term as key
$image_list[$line['cid']]['tags'][$line['term']] = $line['name'];
}
}
}
If I am reading you correctly, this should output exactly what you are looking for.