I would like to add a value to each row that I get from my query depending on if a row exist in another table. Is there a smart way to achieve this?
This is the code I have:
$sth = mysql_query("SELECT tbl_subApp2Tag.*, tbl_tag.* FROM tbl_subApp2Tag LEFT JOIN tbl_tag ON tbl_subApp2Tag.tag_id = tbl_tag.id WHERE tbl_subApp2Tag.subApp_id = '".$sub."' ORDER BY tbl_tag.name ASC");
if(!$sth) echo "Error in query: ".mysql_error();
while($r = mysql_fetch_assoc($sth)) {
$query = "SELECT * FROM tbl_userDevice2Tag WHERE tag_id='".$r['id']."' AND userDevice_id='".$user."'";
$result = mysql_query($query) or die(mysql_error());
if (mysql_num_rows($result)) {
$r['relation'] = true;
$rows[] = $r; //Add 'relation' => true to this row
} else {
$r['relation'] = false;
$rows[] = $r; //Add 'relation' => false to this row
}
}
print json_encode($rows);
Where the //Add ... is, is where I would like to insert the extra value. Any suggestions of how I can do this? I'm still a beginner in PHP so if there are anything else that I have missed please tell me.
EDIT: Second query was from the wrong table. This is the correct one.
Edited Edited below query to reflect new information because I don't like leaving things half-done.
$sth = mysql_query("
SELECT
tbl_subApp2Tag.*,
tbl_tag.*,
ISNULL(tbl_userDevice2Tag.userDevice_id) AS relation
FROM tbl_subApp2Tag
LEFT JOIN tbl_tag
ON tbl_tag.id = tbl_subApp2Tag.tag_id
LEFT JOIN tbl_userDevice2Tag
ON tbl_userDevice2Tag.tag_id = tbl_tag.id
AND tbl_userDevice2Tag.userDevice_id = '".$user."'
WHERE tbl_subApp2Tag.subApp_id = '".$sub."'
ORDER BY tbl_tag.name ASC
");
Though the above feels like the LEFT JOIN
on tbl_tag
is the wrong way around, but it's hard to tell as you are vague on your eventual aim. For example, if I was to assume the following
Then I would do the following instead. The INNER JOIN means that it won't worry about records in tbl_tag
that are not on the requested subApp_id
which in turn will limit the other joins.
$sth = mysql_query("
SELECT
tbl_subApp2Tag.*,
tbl_tag.*,
ISNULL(tbl_userDevice2Tag.userDevice_id) AS relation
FROM tbl_tag
INNER JOIN tbl_subApp2Tag
ON tbl_subApp2Tag.tag_id = tbl_tag.id
AND tbl_subApp2Tag.subApp_id = '".$sub."'
LEFT JOIN tbl_userDevice2Tag
ON tbl_userDevice2Tag.tag_id = tbl_tag.id
AND tbl_userDevice2Tag.userDevice_id = '".$user."'
ORDER BY tbl_tag.name ASC
");
$r['append'] = "value";
before adding $r to the array?
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