WHEREサブクエリを使用してSQLを改善する

Question

少し遅いですが、うまく動作するこのSQLを持っています。理想的には、where句に余分なサブクエリを入れたいと思っています。そして、country_iso = "uk"のようなものです。

SELECT c.content_name, c.content_telephone, c.content_address1 
    (SELECT w.weblink_url FROM weblinks w WHERE w.content_id = c.content_id ORDER BY w.weblink_ordering, w.weblink_id ASC LIMIT 1) 
    AS content_url,               
    (SELECT country_name FROM countries WHERE country_id = c.country_id LIMIT 1) 
    AS country_name,                              
    (SELECT country_iso FROM countries WHERE country_id = c.country_id LIMIT 1) 
    AS country_iso 
    FROM catcontents cc              
    LEFT JOIN content c ON c.content_id = cc.content_id               
    WHERE cc.category_id = 7 
    AND (SELECT country_iso FROM countries WHERE country_id = c.country_id LIMIT 1) = 'uk' 
ORDER BY cc.catcontent_ordering ASC, c.content_name ASC 

Answer 1

この質問はあなたのニーズに合っていませんか？ （基本的には、使用は代わりに、サブセレクトの、国を取得するために結合します。）

SELECT 
    c.content_name, 
    c.content_telephone, 
    c.content_address1, 

    countries.country_name, 
    countries.country_iso, 

    (
     SELECT w.weblink_url 
     FROM weblinks w 
     WHERE w.content_id = c.content_id 
     ORDER BY w.weblink_ordering, w.weblink_id ASC 
     LIMIT 1 
    ) content_url 

FROM catcontents cc 
LEFT JOIN content c ON c.content_id = cc.content_id 
JOIN countries ON countries.country_id = c.country_id 

WHERE cc.category_id = 7 
AND countries.country_iso = 'uk' 

ORDER BY cc.catcontent_ordering ASC, c.content_name ASC 

Answer 2

SELECT c.content_name, 
     c.content_telephone, 
     c.content_address1, 
     w.weblink_url content_url, 
     country_name, 
     country_iso 
FROM catcontents cc              
LEFT JOIN content c ON c.content_id = cc.content_id 
LEFT JOIN weblink_url w ON w.content_id = c.content_id 
JOIN countries ON country_id = c.country_id 
        AND country_iso = 'uk'          
WHERE cc.category_id = 7