1248 - 每个派生表必须有自己的别名

Question

我有一个MYSQL查询，它正常工作，除了我想对两个语句执行OUTER连接，以便它们显示第一个表的行，而不需要在第二个表中有相应的行。查询如下

SELECT wp_usermeta.user_id,
                    m9.id as group_id,
                    wp_usermeta.meta_value as nickname,
                    m2.meta_value as abbreviation,
                    m3.meta_value as name,
                    m4.meta_value as games,
                    m5.description as description,
                    m6.slug as slug,
                    m7.date_created as date_created,
                    m8.meta_value as total_member_count,
                    m10.status as status,
                    m11.membership_id as type
            FROM wp_usermeta 
            INNER JOIN wp_usermeta as m2 ON wp_usermeta.user_id = m2.user_id
            INNER JOIN wp_usermeta as m3 ON wp_usermeta.user_id = m3.user_id
            INNER JOIN wp_usermeta as m4 ON wp_usermeta.user_id = m4.user_id
            INNER JOIN wp_bp_groups as m5 ON wp_usermeta.user_id = m5.creator_id
            INNER JOIN wp_bp_groups as m6 ON wp_usermeta.user_id = m6.creator_id
            INNER JOIN wp_bp_groups as m7 ON wp_usermeta.user_id = m7.creator_id
            INNER JOIN wp_bp_groups as m9 ON wp_usermeta.user_id = m9.creator_id
            INNER JOIN wp_bp_groups_groupmeta as m8 ON m9.id = m8.group_id
          #  INNER JOIN wp_2_pmpro_memberships_users as m10 ON wp_usermeta.user_id = m10.user_id
          #  INNER JOIN wp_2_pmpro_memberships_users as m11 on wp_usermeta.user_id = m11.user_id
            WHERE (wp_usermeta.meta_key = 'nickname' AND 
                    m2.meta_key = 'abbreviation' AND
                    m3.meta_key = 'name' AND
                    m4.meta_key = 'games' AND
                    m8.meta_key = 'total_member_count' AND
                    m10.status  = 'active' AND
                    m11.status  = 'active'
                    )

根据this SO帖子我尝试使用格式

SELECT * FROM t1 
LEFT JOIN t2 ON t1.id = t2.id 
UNION 
SELECT * FROM t1 
RIGHT JOIN t2 ON t1.id = t2.id

将标有＃above的两行更改为

            INNER JOIN (
                    SELECT * FROM wp_usermeta
                    LEFT JOIN wp_2_pmpro_memberships_users ON wp_usermeta.user_id = wp_2_pmpro_memberships_users.user_id
                    UNION
                    SELECT * FROM wp_usermeta
                    RIGHT JOIN wp_2_pmpro_memberships_users ON wp_usermeta.user_id = wp_2_pmpro_memberships_users.user_id
                )

但它似乎不起作用。 MySQL抛出错误

1248 - 每个派生表必须有自己的别名

我的SQL查询知识是基本的，仅限于简单的数据库查询。任何帮助将不胜感激。

Answer 1

在一个表中找到您在另一个表中没有的ID的基本方法是

Select * from t1 where t1.commonid not in(select commonid from t2);

这种方法很有效，但随着桌子的增长而变化非常大。所以更好的方法是

Select t1.* 
FROM t1 left join t2 on t1.commonid = t2.commonid
where t2.id is null

左连接为您提供来自t1的所有行以及来自t2的相应行，来自t1的行（t2中没有对应的行）对于所有t2值返回null。所以只需使用任何t2字段＆＃34; not null＆＃34;集。

Answer 2

在我看来，你只是在这之后：

         SELECT wp_usermeta.user_id,
                m9.id as group_id,
                wp_usermeta.meta_value as nickname,
                m2.meta_value as abbreviation,
                m3.meta_value as name,
                m4.meta_value as games,
                m5.description as description,
                m6.slug as slug,
                m7.date_created as date_created,
                m8.meta_value as total_member_count,
                m10.status as status,
                m11.membership_id as type
        FROM wp_usermeta 
        INNER JOIN wp_usermeta as m2 ON wp_usermeta.user_id = m2.user_id
        INNER JOIN wp_usermeta as m3 ON wp_usermeta.user_id = m3.user_id
        INNER JOIN wp_usermeta as m4 ON wp_usermeta.user_id = m4.user_id
        INNER JOIN wp_bp_groups as m5 ON wp_usermeta.user_id = m5.creator_id
        INNER JOIN wp_bp_groups as m6 ON wp_usermeta.user_id = m6.creator_id
        INNER JOIN wp_bp_groups as m7 ON wp_usermeta.user_id = m7.creator_id
        INNER JOIN wp_bp_groups as m9 ON wp_usermeta.user_id = m9.creator_id
        INNER JOIN wp_bp_groups_groupmeta as m8 ON m9.id = m8.group_id
      #  LEFT JOIN wp_2_pmpro_memberships_users as m10 
                ON wp_usermeta.user_id = m10.user_id
               AND m10.status  = 'active' 

      #  LEFT JOIN wp_2_pmpro_memberships_users as m11 
                ON wp_usermeta.user_id = m11.user_id
               AND m11.status  = 'active'

        WHERE (wp_usermeta.meta_key = 'nickname' AND 
                m2.meta_key = 'abbreviation' AND
                m3.meta_key = 'name' AND
                m4.meta_key = 'games' AND
                m8.meta_key = 'total_member_count' 
                )

需要做一个MySQL OUTER JOIN

1248 - 每个派生表必须有自己的别名

2 个答案: