如何將這2個SQL查詢合併爲一個

Question

我在計算如何組合這兩個查詢時遇到了一些問題。

$get_id = $psk->goqueryvalue("SELECT `categoryid` FROM `products` WHERE `seo_title` = '{$url_title}'"); 

$get_category = $psk->goqueryvalue("SELECT `title` FROM `categories` WHERE `id` = '{$get_id}'"); 

（$ psk-> goqueryvalue只返回一個值。）

感謝

Answer 1

SELECT c.title # also c.id if you need it 
FROM categories c, products p 
WHERE c.id = p.categoryid 
AND p.seo_title = '{$url_title}' 

Answer 2

試着這麼做

SELECT `categoryid`, `title` FROM `products` 
    LEFT JOIN `categories` ON `products`.`categoryid` = `categories`.`id` 
    WHERE `products`.`seo_title` = '{$url_title}' 

Answer 3

試着這麼做

$get_category = $psk->goqueryvalue("SELECT `title` FROM `categories` WHERE `id` = (SELECT `categoryid` FROM `products` WHERE `seo_title` = '{$url_title}'"); 

OR

$get_category = $psk->goqueryvalue("SELECT `title` FROM `categories` INNER JOIN `products` ON 
`categories.id` = `products.categoryid` WHERE `seo_title` = '{$url_title}'");