选择类别

Question

我对以下查询有疑问:(注意，长查询!!）

SELECT
            c.frm_category_id,
            c.name,
            c.slug,
            s.frm_category_id,
            s.name,
            s.slug,
            s.description,
            IFNULL(topics_count,0),
            IFNULL(messages_count,0),
            n.frm_message_id,
            n.user_id,
            n.frm_topic_id,
            n.timestamp,
            n.title,
            n.slug,
            u.account_type,
            u.username
FROM
            frm_categories AS c
LEFT JOIN(
            SELECT
                    frm_category_id,
                    parent_frm_category_id,
                    name,
                    slug,
                    description
            FROM
                    frm_categories
            WHERE
                    parent_frm_category_id != 0
) AS s
            ON
                    c.frm_category_id = s.parent_frm_category_id    
LEFT JOIN(
            SELECT
                    frm_category_id,
                    frm_topic_id,
                    COUNT(frm_topic_id) AS topics_count
            FROM
                    frm_topics
            GROUP BY
                    frm_category_id
) AS t
            ON
                    s.frm_category_id = t.frm_category_id
LEFT JOIN(
            SELECT
                    COUNT(frm_message_id) AS messages_count,
                    frm_topic_id,
                    frm_category_id
            FROM
                    frm_messages
            GROUP BY
                    frm_category_id
) AS m
            ON
                    t.frm_topic_id = m.frm_topic_id
LEFT JOIN(
            SELECT
                    MAX(m.frm_message_id) AS frm_message_id,
                    m.user_id,
                    m.frm_category_id,
                    m.frm_topic_id,
                    m.timestamp,
                    t.title,
                    t.slug
            FROM
                    frm_messages AS m,
                    frm_topics AS t
            WHERE
                    m.frm_topic_id = t.frm_topic_id
            GROUP BY
                    m.frm_topic_id
) AS n
            ON
                    s.frm_category_id = n.frm_category_id
LEFT JOIN
                    users AS u
            ON
                    n.user_id = u.user_id
            WHERE
                    c.parent_frm_category_id = 0
ORDER BY
            c.frm_category_id ASC,
            s.frm_category_id ASC

说明：

SELECT =＆gt;我选择PARENT类别的category_id，name和slug（因为WHERE parent_frm_category_id = 0）

FIRST LEFT JOIN =＆gt;我选择父类别的子类别（超过1）

SECOND LEFT JOIN =＆gt;我计算每个子类别中的所有主题

THIRD LEFT JOIN =＆gt;我计算每个子类别中的所有消息

第四个左加入=＆gt;我选择每个子类别的最后一条消息（出错的地方）

第五个LEFT JOIN =＆gt;我选择每个子类别的最后一条消息的account_type和username

问题是什么？

我没有选择最后一条消息，而是一条随机消息。

有人可以帮我吗？ ：）

提前致谢！

Answer 1

这是否能满足您的需求：

@For /f "Delims=:" %A in ('tasklist /nh /v /fi "WINDOWTITLE eq Headphones"') do @if %A==INFO (echo Prog not running) else (start /min "audiorepeater_ks" "c:program files\Virtual Audio Cable\audiorepeater_ks.exe" /CloseInstance: Headphones)