mysql - 来自另一个子选择的子选择字段有什么问题？

Question

我的 table 是:

• tbl_activity(id, 名称)
• tbl_activity_package(id、activity_id、名称)
• tbl_activity_package_address(id，activity_package_id，地区)

用户给出一个地区，我返回该地区发生的事件列表。根据事件可能有多个地区，因此我稍后必须通过 GROUP_CONCAT() 返回它。

SELECT a.name, ap.name
FROM (
    SELECT apa_inner.activity_package_id AS activity_package_id
    FROM tbl_activity_package_address AS apa_inner
    WHERE district = 'Beja'
) AS apa
INNER JOIN (
    SELECT ap_inner.id, ap_inner.name, ap_inner.activity_id
    FROM tbl_activity_package_address AS apa_inner
    INNER JOIN tbl_activity_package AS ap_inner ON ap_inner.id = apa.activity_package_id
) AS ap ON apa.activity_package_id = ap.id
INNER JOIN tbl_activity AS a ON a.id = ap.activity_id

这给了我错误:“'on'子句中的未知列'apa.activity_package_id'”。

<小时/>

SELECT a.name, ap.name
FROM (
    SELECT id, activity_package_id
    FROM tbl_activity_package_address AS apa_inner
    WHERE district = 'Beja'
) AS apa
INNER JOIN (
    SELECT ap_inner.id AS id, ap_inner.name, ap_inner.activity_id
        FROM tbl_activity_package_address AS apa_inner
        INNER JOIN tbl_activity_package AS ap_inner ON ap_inner.id = apa_inner.activity_package_id
        WHERE apa_inner.id = apa.id
) AS ap ON apa.activity_package_id = ap.id
INNER JOIN tbl_activity AS a ON a.id = ap.activity_id

这给了我错误:“where 子句中存在未知列 'apa.id'”。

Answer 1

旧答案

在第二个子选择中，您使用别名 apa_inner 和 ap_inner 所以

SELECT a.name, ap.name
FROM (
    SELECT apa_inner.activity_package_id AS activity_package_id
    FROM tbl_activity_package_address AS apa_inner
    WHERE district = 'Beja'
) AS apa
INNER JOIN (
    SELECT ap_inner.id AS id
        FROM tbl_activity_package_address AS apa_inner
        INNER JOIN tbl_activity_package AS ap_inner ON ap_inner.id = apa_inner.activity_package_id
) AS ap ON apa.activity_package_id = ap.id
INNER JOIN tbl_activity AS a ON a.id = ap.activity_id

应该修复错误。但你真的需要这些子选择吗？我相信您可以简化这个查询。

<小时/>

新答案

来自

tbl_activity(id, name) tbl_activity_package(id, activity_id, name) tbl_activity_package_address(id, activity_package_id, district)

结果应生成具有某个包裹地址位于某个地区的所有包裹的所有事件，以及该事件涵盖的所有地区的列表。

这个查询就可以了

SELECT
    a.name,
    GROUP_CONCAT(DISTINCT apa.district ORDER BY apa_district) AS distritos
FROM
    tbl_activity a
INNER JOIN
    tbl_activity_package ap
ON
    a.id = ap.activity_id
INNER JOIN
    tbl_activity_package_address apa
ON
    ap.id = apa.activity_package_id 
WHERE a.id IN (
    SELECT 
        ap_inner.activity_id
    FROM
        tbl_activity_package AS ap_inner
    INNER JOIN
        tbl_activity_package_id apa_inner
    ON
        ap_inner.id = apa_inner.activity_package_id 
    WHERE    
        apa_inner.district = 'Beja'
)       
GROUP BY 
    a.name