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我有这两个查询

select 
    t . *, events.event_time as last_time
from
    events,
(
    (
        select 
            bonding.type,
                bonding.global_id2 as target_post,
                bonding.target_id as on_whose_post,
                GROUP_CONCAT(bonding.shooter_id) as shooter_ids,
                GROUP_CONCAT(bonding.what_global_id) as shooted_what,
                MAX(bonding.what_global_id) as last,
                'bonding' as flag
        from
            bonding
        where
            bonding.type = 1
                and bonding.shooter_id in (select 
                    `user2`
                from
                    relation_table
                where
                    `user1` = 192)
        group by bonding.global_id2
    ) 
    union 
    (
    select 
            bonding.type,
                bonding.global_id2 as target_post,
                bonding.target_id as on_whose_post,
                GROUP_CONCAT(bonding.shooter_id) as shooter_ids,
                GROUP_CONCAT(bonding.what_global_id) as shooted_what,
                MAX(bonding.what_global_id) as last,
                'bonding' as flag
        from
            bonding
        where
            bonding.type = 2
                and bonding.shooter_id in (select 
                    `user2`
                from
                    relation_table
                where
                    `user1` = 192)
        group by bonding.global_id2
    ) 
    union 
    (
    select 
            bonding.type,
                bonding.global_id2 as target_post,
                bonding.target_id as on_whose_post,
                GROUP_CONCAT(bonding.shooter_id) as shooter_ids,
                GROUP_CONCAT(bonding.what_global_id) as shooted_what,
                MAX(bonding.what_global_id) as last,
                'bonding' as flag
        from
            bonding
        where
            bonding.type = 5
                and bonding.shooter_id in (select 
                    `user2`
                from
                    relation_table
                where
                    `user1` = 192)
        group by bonding.global_id2
    ) 
    union 
    (
    select 
            bonding.type,
                bonding.global_id2 as target_post,
                bonding.target_id as on_whose_post,
                GROUP_CONCAT(bonding.shooter_id) as shooter_ids,
                GROUP_CONCAT(bonding.what_global_id) as shooted_what,
                MAX(bonding.what_global_id) as last,
                'bonding' as flag
        from
            bonding
        where
            bonding.type = 9
                and bonding.shooter_id in (select 
                    `user2`
                from
                    relation_table
                where
                    `user1` = 192)
        group by bonding.global_id2
    ) 
    union 
    (
    select 
            bonding.type,
                bonding.global_id2 as target_post,
                bonding.target_id as on_whose_post,
                GROUP_CONCAT(bonding.shooter_id) as shooter_ids,
                GROUP_CONCAT(bonding.what_global_id) as shooted_what,
                MAX(bonding.what_global_id) as last,
                'bonding' as flag
        from
            bonding
        where
            bonding.type = 10
                and bonding.shooter_id in (select 
                    `user2`
                from
                    relation_table
                where
                    `user1` = 192)
        group by bonding.global_id2
    )

)as t where events.global_id = t1.last

还有一个：-

SELECT 
    post_stream.type,
    post_stream.ref_global_id as target_post,
    post_stream.user_id as on_whose_post,
    post_stream.user_id as shooter_ids,
    post_stream.ref_global_id as shooted_what,
    post_stream.ref_global_id as last,
    'stream' as flag,
    events.event_time as last_time
FROM
    post_stream,
    events,
    relation_table
WHERE
    events.global_id = post_stream.ref_global_id
        and post_stream.type IN (2 , 3, 7, 8)
        AND post_stream.user_id = relation_table.user2
        AND relation_table.user1 = 192

现在我需要对两个查询执行连接以获得组合结果，但是它给出了每个派生表都必须有自己的别名错误，我应该为派生表放置一个别名，这两个查询在单独运行时运行时没有错误.

4

1 回答 1

1

第一个查询的格式大约有 116 行，并且包含一个 5 路 UNION 子查询。除了 WHERE 子句中的一个值之外，这 5 个子查询似乎是相同的。这种重写极大地简化了 SQL：

SELECT t.type, t.target_post, t.on_whose_post, t.shooter_ids, t.shooted_what,
       t.last, t.flag, events.event_time AS last_time
  FROM events JOIN
       (SELECT bonding.type,
               bonding.global_id2 AS target_post,
               bonding.target_id AS on_whose_post,
               GROUP_CONCAT(bonding.shooter_id) AS shooter_ids,
               GROUP_CONCAT(bonding.what_global_id) AS shooted_what,
               MAX(bonding.what_global_id) AS last,
               'bonding' AS flag
          FROM bonding
         WHERE bonding.TYPE IN (1, 2, 5, 9, 10)
           AND bonding.shooter_id IN (SELECT user2 FROM relation_table WHERE user1 = 192)
         GROUP BY bonding.global_id2
        ) AS t
     ON events.global_id = t1.last

这将更容易与第二个查询结合使用。随着进一步的修订，我可能会删除bonding.前缀，因为主子查询中唯一的表是bonding.

第二个查询也应该使用 JOIN 表示法重写：

SELECT p.type          AS type,
       p.ref_global_id AS target_post,
       p.user_id       AS on_whose_post,
       p.user_id       AS shooter_ids,
       p.ref_global_id AS shooted_what,
       p.ref_global_id AS last,
       'stream'        AS flag,
       e.event_time    AS last_time
  FROM post_stream    AS p
  JOIN events         AS e ON e.global_id = p.ref_global_id
  JOIN relation_table AS r ON p.user_id = r.user2
 WHERE r.user1 = 192
   AND post_stream.type IN (2 , 3, 7, 8)

问题：

  1. 您确定on_whose_post并且shooter_ids应该来自同一列吗？
  2. 您确定shooted_what并且last应该来自同一列吗？

这样做可能有正当的（而且不是太牵强）的理由——但这并不是立即显而易见的。

不幸的是，我们还没有被告知如何将上面第一个查询中的数据与第二个查询连接起来。似乎有很多相同的列；只有 OP 才能确定需要什么。

于 2012-11-25T13:12:49.427 回答