Question

如果我从下面的语句中删除ORDER BY c.campaign_id ASC它可以正常工作，但现在它会抛出Sub query return more than 1 row。

SELECT SQL_CALC_FOUND_ROWS c.campaign_id, 
    c.title as campaign_title,
    IFNULL((SELECT meta_value 
            FROM campaign_meta as cm
            WHERE cm.campaign_id = c.campaign_id 
            AND cm.meta_key = 'total_viewed'), 0) AS total_viewed, 
    c.campaign_identifier, 
    c.added_datetime,
    l.label_id, 
    l.title AS label_title, 
    l.color, 
    u.username 
FROM campaigns AS c 
LEFT JOIN users AS u ON u.user_id = c.author
LEFT JOIN campaign_relation AS cr ON c.campaign_id = cr.campaign_id
LEFT JOIN labels AS l ON l.label_id = cr.label_id
ORDER BY c.campaign_id ASC
LIMIT 0, 10

Answer 1

您的子查询返回的结果多了一行

(SELECT meta_value FROM campaign_meta as cm WHERE cm.campaign_id = c.campaign_id AND
cm.meta_key = 'total_viewed')

我们需要更改您的查询以使用sytax：

SELECT ... LIMIT 1

为MySQL更新它

   (SELECT meta_value FROM campaign_meta as cm WHERE cm.campaign_id = c.campaign_id AND
    cm.meta_key = 'total_viewed' LIMIT 1)

或重写查询

对MS SQL语法感兴趣

(SELECT TOP 1 meta_value FROM campaign_meta as cm WHERE cm.campaign_id = c.campaign_id AND
cm.meta_key = 'total_viewed')

这个SQL查询我做错了什么？

1 个答案: