SQL联接多个表& Get AVG

Question

我正尝试在我的sql查询中执行几个连接，但遇到了问题。我需要做的是从poker_sites表中选择所有字段，然后从networks中获取2个相对字段，如果可用，则从editor_content获取平均评级

我遇到的问题是，查询只返回一行，而实际上应该至少有三行。

任何帮助都将不胜感激。

下面是我的SQL

SELECT AVG(editor_content.rating) AS rating, poker_sites.*,
networks.network_name, networks.network_icon FROM poker_sites
    LEFT JOIN networks
    ON (poker_sites.network_id=networks.network_id)
    LEFT JOIN editor_content
    ON (poker_sites.site_id=editor_content.assign_id)
    WHERE poker_sites.published=1

Answer 1

如果您想通过一个聚合函数(在本例中为AVG)获得多个结果，则需要GROUP BY。

    SELECT x.avgRating AS rating, poker_sites.*,
        networks.network_name, networks.network_icon 
    FROM poker_sites
    LEFT JOIN networks
        ON (poker_sites.network_id=networks.network_id)
    LEFT JOIN 
    (
        SELECT AVG(editor_content.rating) as avgRating, editor_content.assign_id
        FROM editor_content
        GROUP BY editor_content.assign_id
    ) x
        ON (poker_sites.site_id = x.assign_id)
    WHERE poker_sites.published=1