Why is my 3 table JOIN MySQL query not working? - php

Question

I have 3 tables:
Table: album
Columns: id, name, description, author, path, image
Table: albumconnect
Columns: id, imageid, albumid
Table: albumimages
Columns: id, path
And I'm trying to replace all those unnecessary queries with a single JOIN query:
<?php
$albumID = $_SERVER['QUERY_STRING'];
$realAlbumID = substr($albumID, 1);
$realestAlbumID = str_replace('%20', ' ', $realAlbumID);
$sql = "SELECT * FROM album WHERE id='$realestAlbumID'";
$result = mysqli_query($conn, $sql);
$getResult = mysqli_fetch_assoc($result);
$albumPath = $getResult['path'];
$sql2 = "SELECT * FROM albumconnect WHERE albumid='$realestAlbumID'";
$result2 = mysqli_query($conn, $sql2);
while ($row = $result2->fetch_assoc()){
$imageId = $row['imageid'];
$sql3 = "SELECT * FROM albumimages WHERE id='$imageId'";
$result3 = mysqli_query($conn, $sql3);
$getResult3 = mysqli_fetch_assoc($result3);
$imagePath = $getResult3['path'];
echo '<div class="imageContainerAlbums"><li class="listAlbums"><img class="specificAlbumThumnails" src="'.$albumPath.$imagePath.'" alt="Random image" /></li></div>';
};
?>
Now the JOIN query I've come up with based on stuff I've read online is this:
$sql5 = "SELECT * FROM album
JOIN albumconnect ON albumconnect.albumid=album.id
JOIN albumimages ON albumimages.id=albumconnect.imageid
WHERE id='$realestAlbumID'";
$result5 = mysqli_query($conn, $sql5);
However, when I try to var_dump the contents, it prints Null so I assume my query is incorrect but I can't figure out the correct way to do it.

Answer 1

Should be something like this. I didn't test it. As #Difster correctly said, SQL engine doesn't know which id should it reference. So, define table aliases and prefix the referenced columns with them. Then define unique aliases for the column names too. Otherwise your sql statement were almost perfect.
<?php
$albumID = $_SERVER['QUERY_STRING'];
$realAlbumID = substr($albumID, 1);
$realestAlbumID = str_replace('%20', ' ', $realAlbumID);
$sql = "SELECT
alb.name AS album_name,
alb.description AS album_description,
alb.author AS album_author,
alb.path AS album_path,
alb.image AS album_image,
ali.path AS image_path
FROM album AS alb
LEFT JOIN albumconnect AS alc ON alc.albumid = alb.id
LEFT JOIN albumimages AS ali ON ali.id = alc.imageid
WHERE alb.id = '$realestAlbumID'";
$result = mysqli_query($conn, $sql);
while ($row = $result->fetch_assoc()) {
$albumPath = $row['album_path'];
$imagePath = $row['image_path'];
echo '<div class="imageContainerAlbums">';
echo '<li class="listAlbums">';
echo '<img class="specificAlbumThumnails" src="' . $albumPath . $imagePath . '" alt="Random image" />';
echo '</li>';
echo '</div>';
}
EDIT 1:
The columns from the sql statement which you don't use later are optional. So, you don't need to select all columns if you don't need them later.
It maybe that you are also becoming rows with NULL values for alc or ali tables. It means that not all albums have images. Then you must give us values you have in the tables, so that we can provide you the proper further WHERE conditions like WHERE ali IS NOT NULL. This answer of me is just the starting point for you.
EDIT 2:
This version is ok too. I just changed the sql statement.
<?php
$albumID = $_SERVER['QUERY_STRING'];
$realAlbumID = substr($albumID, 1);
$realestAlbumID = str_replace('%20', ' ', $realAlbumID);
$sql = "SELECT
alb.name AS album_name,
alb.description AS album_description,
alb.author AS album_author,
alb.path AS album_path,
alb.image AS album_image,
ali.path AS image_path
FROM albumimages AS ali
LEFT JOIN albumconnect AS alc ON alc.imageid = ali.id
LEFT JOIN album AS alb ON alb.id = alc.albumid
WHERE alb.id = '$realestAlbumID'";
$result = mysqli_query($conn, $sql);
while ($row = $result->fetch_assoc()) {
$albumPath = $row['album_path'];
$imagePath = $row['image_path'];
echo '<div class="imageContainerAlbums">';
echo '<li class="listAlbums">';
echo '<img class="specificAlbumThumnails" src="' . $albumPath . $imagePath . '" alt="Random image" />';
echo '</li>';
echo '</div>';
}