Question

我想对连接表中的值使用where语句。无法理解：

SELECT item.*, count(articles.authorid) AS articlecount 
FROM #_authors AS item 
LEFT JOIN #_articles AS articles ON (articles.authorid = item.id) 
WHERE item.published=1 
AND articlecount>3 
ORDER BY articlecount DESC

orderby工作正常，但当我添加“AND articlecount＆gt; 3”时，我收到错误：“＃1054 - 'where子句'中的未知列'articlecount'。”

将WHERE包含在关键字中的最佳方法是什么？提前谢谢！

Answer 1

对于汇总列，您使用HAVING，如下所示：

SELECT item.*, count(articles.authorid) AS articlecount 
FROM #_authors AS item 
LEFT JOIN #_articles AS articles ON (articles.authorid = item.id) 
WHERE item.published=1 
GROUP BY 1,2,3,4,5,6,7,8 -- assuming there are 8 columns in item
HAVING count(articles.authorid) > 3 
ORDER BY 9 DESC -- assuming there are 8 columns in item

Answer 2

 SELECT item.*, count(articles.authorid) AS articlecount 
    FROM #_authors AS item 
    LEFT JOIN #_articles AS articles ON (articles.authorid = item.id) 
    WHERE item.published=1 
    AND articlecount>3 
    ORDER BY articlecount DESC


articlecount refers to which table field?
if articlecount  is in #_author table then you have to write item.articlecount 

or articles.articlecount

Answer 3

尝试使用HAVING按汇总的valeus进行过滤：

WHERE item.published=1
HAVING count(articles.authorid) > 3
ORDER BY articlecount DESC

在where子句中使用join值

3 个答案: