Searching multiple databases to output lowest value - php

Question

$query = mysqli_query($mysqli, "SELECT product_name ,MIN(product_price) product_price,link FROM(
select jumia.product_name,jumia.product_price,jumia.product_image,jumia.link from jumia INNER JOIN
jumia ON jumia.id = olx.id
where product.name like '%{$search}%'
UNION
select olx.product_name,olx.product_price,olx.product_image, olx.link from olx INNER JOIN
olx ON olx.id = jumia.id
where product.name like '%{$search}%')Minim
GROUP BY product_name,product_image
");
I am trying to create a query from two tables with similar column names as displayed above that will allow me to display the rows between the two tables that have the lowest price.
For example, if product_name called mattresses is searched the matching item in my database whose price is lower between the two table names should be displayed. Some help would be appreciated

Answer 1

I think this is the general idea of what you're trying to do:
SELECT id, price
FROM (SELECT id, price FROM T1 WHERE price = (SELECT min(price) FROM T1)
UNION
SELECT id, price FROM T2 WHERE price = (SELECT min(price) FROM T2)
) AS M
ORDER BY price ASC
LIMIT 1

Answer 2

Ended up changing the code and removing the ordering at the end and this finally worked. I hadn't properly linked my database using foreign keys, and changed my code to reflect this.
$query = mysqli_query($mysqli, "
SELECT product_name
, MIN(product_price) product_price
, link
FROM
( select j.product_name
, j.product_price
, j.link
from jumia j
JOIN olx
ON j.categoryID = olx.categoryID
where j.product_name like '%{$search}%'
UNION select olx.product_name
, olx.product_price
, olx.link
from olx
JOIN jumia
ON jumia.categoryID = olx.categoryID
where olx.product_name like '%{$search}%'
) x
");