How do I join 4 tables on mysql select statement? - php

Question

I have 4 tables in MySQL to join. Example
$select = $db->query("SELECT *
FROM ads
WHERE ad_pic='1'
AND ad_status = '1'
ORDER BY ad_id DESC LIMIT 0,4");
while ($fetch = $db->fetch($select)) {
$iquery = $db->query("SELECT *
FROM images
WHERE img_ads_id = '" . intval($fetch['ad_id']) . "'
AND img_status = '1'
LIMIT 1");
$thumb = $db->fetch($iquery);
$uselect = $db->query("SELECT *
FROM users
WHERE user_id = '".intval($fetch['ad_userid'])."'
AND user_status = '1'
LIMIT 1");
$ufetch = $db->fetch($uselect);
$cselect = $db->query("SELECT *
FROM category
WHERE cat_slug = '".safe_func($fetch['ad_category'])."'
LIMIT 1");
$cfetch = $db->fetch($cselect);
}
I want to know the way to join these in one select statement.
ads table
ad_id ad_userid ad_category
-------------------------------
1 2 5
images table
img_id img_ads_id
-------------------------------
1 1
users table
user_id user_name
-------------------------------
2 John
category table
cat_id cat_name
-------------------------------
5 Vehicles

Answer 1

SELECT *
FROM ads AS a
LEFT JOIN images AS i ON i.img_ads_id = a.ad_id AND i.img_status = 1
LEFT JOIN users AS u ON u.id = a.ad_userid AND u.user_status = 1
LEFT JOIN category AS c ON c.cat_slug = a.ad_category
WHERE a.ad_pic = 1
AND a.ad_status = 1
ORDER BY a.ad_id DESC
LIMIT 0,4
If an ad must have an image, user, or category, you may use a JOIN instead of a LEFT JOIN. If an ad can have more than one image, user, or category, you will need a more complex query.