How do output combined results from two MySQL tables using PDO - php

Question

I have the following two table structures in MySQL, which record details of a conference call and those participants that joined it:
Table: conference:
conference_sid, date_created, date_completed, RecordURL, PIN
*date_created and *date_completed are timestamps
Table: participants:
conference_sid, call_sid, call_from, name_recording
I want to output a simple table, that displays the following results for each conference_sid as a separate row:
<table>
<thead>
<th>Date</th>
<th>Duration</th>
<th>Participants</th>
<th>Recording</th>
</thead>
<tbody>
<tr id="conference_sid">
<td>date_created</td>
<td>duration: [date_completed - date_created in h/mm/ss]</td>
<td>
<li>call_from [for all participants in that conference_sid]
<li>call_from...
</td>
<td>
Call recording
</td>
</tr>
<tr id="conference_sid">
...
</tr>
</tbody>
</table>
I only want this table to show relevant results for conferences that have the same PIN as the user's Session::get('PIN')

Answer 1

You can combine the participants using GROUP_CONCAT
SELECT
conf.conference_sid,
date_created,
TIMEDIFF(date_completed, date_created) AS duration,
conf.RecordURL,
conf.PIN,
GROUP_CONCAT(pid SEPARATOR ",") AS pid,
GROUP_CONCAT(call_sid SEPARATOR ",") AS call_sid,
GROUP_CONCAT(call_from SEPARATOR ",") AS call_from,
GROUP_CONCAT(name_recording SEPARATOR ",") AS name_recording
FROM
conference conf
LEFT OUTER JOIN
participants p ON p.conference_sid = conf.conference_sid
WHERE
conf.PIN = 123
GROUP BY conf.conference_sid
Refer SQLFIDDLE and MySQL documentation about TIMEDIFF.
Now the application logic will be
<?php
$pin = 123;
$db = new PDO('mysql:host=localhost;dbname=test', 'username', 'password');
$stmt = $db->prepare(
'SELECT
conf.conference_sid,
date_created,
timediff(date_completed, date_created) AS duration,
conf.RecordURL,
conf.PIN,
GROUP_CONCAT(pid SEPARATOR ",") AS pid,
GROUP_CONCAT(call_sid SEPARATOR ",") AS call_sid,
GROUP_CONCAT(call_from SEPARATOR ",") AS call_from,
GROUP_CONCAT(name_recording SEPARATOR ",") AS name_recording
FROM
conference conf
LEFT OUTER JOIN
participants p ON p.conference_sid = conf.conference_sid
WHERE
conf.PIN = :pin
GROUP BY conf.conference_sid');
$stmt->bindParam(':pin', $pin);
?>
<table border="1">
<thead>
<th>Date</th>
<th>Duration</th>
<th>Participants</th>
<th>Recording</th>
</thead>
<tbody>
<?php
$stmt->execute();
while ($row = $stmt->fetch()) {
?>
<tr>
<td><?php echo $row['date_created']; ?></td>
<td><?php echo $row['duration']; ?></td>
<td>
<table border="1">
<thead>
<th>call_sid</th>
<th>call_from</th>
<th>name_recording</th>
</thead>
<tbody>
<?php
$length = count(explode(',', $row['pid']));
$call_sid = explode(',', $row['call_sid']);
$call_from = explode(',', $row['call_from']);
$name_recording = explode(',', $row['name_recording']);
for ($i=0; $i < $length; $i++) {
?>
<tr>
<td> <?php echo $call_sid[$i]; ?> </td>
<td> <?php echo $call_from[$i]; ?></td>
<td> <?php echo $name_recording[$i]; ?> </td>
<tr>
<?php
}
?>
</tbody>
</table>
</td>
<td>
<a href="<?php echo $row['RecordURL']; ?>">
Call recording</a>
</td>
</tr>
<?php
}
?>
</tbody>
You will get the result set with comma(,) separated values in pid, call_sid, call_from, and name_recording. You can convert this string to array using explode.
array explode ( string $delimiter , string $string [, int $limit ] )
Returns an array of strings, each of which is a substring of string
formed by splitting it on boundaries formed by the string delimiter.

Answer 2

I won't do the PHP part, as I am not that knowledgeable in PHP, but here is the SQL:
SELECT *
FROM `conference`, `participants`
WHERE `conference`.PIN = $PIN AND
`participants`.conference_sid = `conference`.conference_sid
This will return rows with the information from conference and the participants of those conferences, joined into one row.

Answer 3

The following query will give you the information you need to display:
SELECT c.conference_sid
, c.date_created
, timediff(c.date_completed, c.date_created) AS duration
, p.call_from
, p.name_recording
, c.RecordURL
FROM conference c
JOIN participants p
ON c.conference_sid = p.conference_sid
WHERE c.PIN = :PIN
ORDER BY c.conference_sid
You will need to process the results with a nested loop. The outer loop should advance each time the conference_sid changes. The inner loop will display each element of the participants list for that conference.

Answer 4

This will be my take on it, it uses 2 separate queries to keep the data kinda separated. I use fetchAll() for brevity but this could have performance issues, luckily this can be accomodated. I didn't put any error checking, if you want it or you have questions, please ask
<?php
// assume $db is a PDO connection to the database
/* #var $db PDO */
$q = 'SELECT conference_sid, date_created, date_completed, RecordURL, PIN'
.' FROM conference';
// we need these
$conferences = $db->query($q)->fetchAll(PDO::FETCH_CLASS,'stdClass');
// let's group them as CSV, and concatenate the contents with ":"
$q = 'SELECT conference_sid,GROUP_CONCAT(CONCAT_WS(":",call_from,name_recording)) AS parts '
.' FROM participants GROUP BY conference_sid';
$conf_parts = array();
foreach ($db->query($q)->fetchAll(PDO::FETCH_CLASS,'stdClass') as $parts) {
// save the participants as an array, their data is still joined though
$conf_parts[$parts->conference_sid] = explode(',',$parts->parts);
// their contents will be exploded later
}
?>
<table>
<thead><th>Date</th><th>Duration</th><th>Participants</th><th>Recording</th></thead>
<tbody><?php foreach ($conferences as $conference) {
$csid = $conference->conference_sid;
// http://stackoverflow.com/questions/3108591/calculate-number-of-hours-between-2-dates-in-php
// Create two new DateTime-objects...
$date1 = new DateTime($conference->date_completed);
$date2 = new DateTime($conference->date_created);
// The diff-methods returns a new DateInterval-object...
$diff = $date2->diff($date1);
?><tr id="<?php echo $csid; ?>">
<td><?php echo $conference->date_created; ?></td>
<td><?php echo $diff->format('H/i/s'); ?></td>
<td>
<ul><?php foreach ($conf_parts[$csid] as $participant) {
// we have each participant for this conference call
list ($call_from, $name_recording) = explode($participant,':');
// and now we have the required data from each participant
?><li><?php echo $call_from; ?></li><?php
} ?></ul>
</td>
<td>
Call recording
</td>
</tr><?php
} ?></tbody>
</table>

Answer 5

In this particular contex I prefer to use two separated queries. Here's how I would do it:
<?php
try {
$db = new PDO('mysql:host=localhost;dbname=test', 'username', 'password');
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException $e) {
echo 'Could not connect to db';
exit;
}
$stmt_conferences = $db->prepare(
'SELECT
date_created,
timediff(date_completed, date_created) AS duration,
RecordURL,
conference_sid
FROM
conference
WHERE
PIN=:pin');
$stmt_conferences->bindParam(':pin', $pin);
$stmt_participants = $db->prepare(
'SELECT
name_recording,
call_from
FROM
participants
WHERE
conference_sid=:confsid');
$stmt_participants->bindParam(':confsid', $confsid);
?>
<table>
<thead>
<th>Date</th>
<th>Duration</th>
<th>Participants</th>
<th>Recording</th>
</thead>
<tbody>
<?php
$pin = 1; /* get your PIN here */
$stmt_conferences->execute();
while ($row = $stmt_conferences->fetch()) {
?>
<tr>
<td><?php echo htmlspecialchars($row['date_created'], ENT_QUOTES); ?></td>
<td><?php echo htmlspecialchars($row['duration'], ENT_QUOTES); ?></td>
<td>
<?php
$confsid = $row['conference_sid'];
$stmt_participants->execute();
while ($participant = $stmt_participants->fetch()) {
?>
<li><a href="<?php echo htmlspecialchars($participant['name_recording'], ENT_QUOTES); ?>">
<?php echo htmlspecialchars($participant['call_from'], ENT_QUOTES); ?>
</a>
<?php
}
?>
</td>
<td>
<a href="<?php echo htmlspecialchars($row['RecordURL'], ENT_QUOTES); ?>">
Call recording</a>
</td>
</tr>
<?php
}
?>
</tbody>
Please notice that you have to add some code to handle errors and to correctly escape all data you echo (can you really trust your database?). Also element IDs should be unique within the entire document, you can have just one id="conference_sid" in your page. Use classes instead.
Edit
If you can really trust your database, then you can just output the contents of a field with code like this:
<?php echo $row['call_from']; ?>
but what happens if RecordURL contains for example the following string?
<script>alert("I am injecting some code....");</script>
It will happen that some unwanted code will be injected in your page, so it is always better yo use a safe function like htmlspecialchars() every time you need to echo some output:
<?php echo htmlspecialchars($row['call_from'], ENT_QUOTES); ?>
this way, any unwanted code won't be harmful.
I also added a basic TRY/CATCH construct to handle errors.
Hope this helps!

Answer 6

First, we need to get our result.
$vPIN = $_SESSION['PIN']; // or however you get your user's pin from session
$vQuery = "SELECT * FROM conference AS a LEFT JOIN participants as B USING (conference_sid) WHERE a.PIN='$vPIN'";
$oResult = $oDB->execute($vQuery);
$aRows = $oResult->fetchAll(PDO::FETCH_ASSOC);
note the prefixes: $v if for a simple variable, $o represents a ressource (which I like to think of as an object), $a represents an array. It's just for my mental sanity.
so now, we have an array, probably very big, containing every single row in the conference table times every corresponding row in the participants. Sweet, now let's build an array with some meaning in it.
foreach($aRows as $aRow) // maybe a bit confusing but the 's' changes everything: all rows vs one row
{if (!isset($aConferences[$aRow['conference_sid']]['infos']))
{$aConferences[$aRow['conference_sid']]['infos']['date_created'] = $aRow['date_created'];
$aConferences[$aRow['conference_sid']]['infos']['date_completed'] = $aRow['date_completed'];
$aConferences[$aRow['conference_sid']]['infos']['record_url'] = $aRow['RecordURL'];
$aConferences[$aRow['conference_sid']]['infos']['pin'] = $aRow['PIN'];}
$aConferences[$aRow['conference_sid']]['participants'][] = $aRow['call_from'];}
so what happens here is that for each row, if the infos for corresponding conference_sid haven't been set, they will be, and then we create a list from 0 to x of each call_from for that conference. print_r of that array with dummy values:
[1627]['infos']['date_created'] = 2013-11-26
['date_completed'] = 2013-11-29
['record_url'] = 'http://whatever.com'
['PIN'] = 139856742
['participants'][0] = Bob
[1] = gertrude
[2] = Foo
[8542]['infos']['date_created'] = 2013-12-01
['date_completed'] = 2013-12-02
['record_url'] = 'http://whateverelse.com'
['PIN'] = 584217
['participants'][0] = Family Guy
[1] = aragorn
[2] = obama
[3] = Loki
so here is a nice array with which we can build a html table! let's do that
$vHTML = '<table>
<thead>
<th>Date</th>
<th>Duration</th>
<th>Participants</th>
<th>Recording</th>
</thead>
<tbody>';
foreach ($aConferences as $conference_sid => $aConference) // notice the s and no s again
{$vHTML.= '<tr id="' . $conference_sid . '">';
$vDateCreated = $aConference['infos']['date_created'];
$vDateCompleted = $aConference['infos']['date_completed'];
$vHTML.= '<td>' . $vDateCreated . '</td>';
$vHTML.= '<td>' . date('Y-m-d',(strtotime($vDateCompleted) - strtotime($vDateCreated))) . '</td>'; // you might have to debug that date diff for yourself.
$vHTML.= '<td><ul>'; // here a foreach for the participants
foreach ($aConference['participants'] as $call_from)
{$vHTML.= '<li>' . $call_from . '</li>';}
$vHTML.= '</ul></td>';
$vHTML.= '<td>' . $aConference['infos']['record_url'] . '</td>';
$vHTML.= '</tr>';}
$vHTML.= '</tbody></table>';
so here: for each conference create a table row with the infos, then for each participant, add a list item within the list. comment if you wish for any precision.
oh, and don't forget to do something with $vHTML. like echo $vHTML :)