如何获取两个单独的 sql 查询的 UNION 并仅获取 DISTINCT 值

Question

如何在 PHP 中仅从我的这两个查询中获取不同的值：

$query1 = "SELECT g.name, g.hash, g.views
                    FROM c7_groups g, c7_groups_affiliations ga
                    WHERE g.category >= 592 AND g.category <= 622
                        AND ga.affiliated_groups_hash = g.hash
                        AND LOWER(g.name) LIKE LOWER('%$school_name%')
                        ";
        $query2 = "SELECT g.name, g.hash, g.views
                    FROM c7_groups g, c7_groups_affiliations ga, c7_affiliations a
                    WHERE ga.affiliations_id = a.id
                        AND ga.groups_hash = g.hash
                        AND LOWER(a.name) LIKE LOWER('%$school_name%')";

我只想从这两个查询中获取不同的“g.hash”。如果我可以有一个可以同时完成这两项任务的 sql 查询，那就更好了。

关于我的数据库表的详细信息如下： c7_groups： id int(10)
名称 varchar(255)
哈希 varchar(32) groups_categories_id int(10) 视图 int(10)

c7_affiliations id int(10) 名称 varchar(100)
groups_categories_id int(10)

c7_groups_affiliations groups_hash varchar(32) 附属的_groups_hash varchar(32)--------FKey to c7_groups.hash
affiliations_id int(10)--------C7_affiliations.id 的 FKey
id int(10)

affiliated_groups_hash 和 affiliations_id 都可以为空，或者我应该说其中一个或它们始终为空。如果一个群组隶属于另一个群组，则 affiliations_id 将为空，如果该群组隶属于另一个联盟，则affiliated_groups_hash 将为空。

如果您需要有关任何事情的更多详细信息，请告诉我。

问候 泽山

Answer 1

只需在子选择中进行联合，然后按派生表分组。

select name,count(*) from
(
               SELECT g.name, g.hash, g.views
                    FROM c7_groups g, c7_groups_affiliations ga
                    WHERE g.category >= 592 AND g.category <= 622
                        AND ga.affiliated_groups_hash = g.hash
                        AND LOWER(g.name) LIKE LOWER('%$school_name%')
     UNION
               SELECT g.name, g.hash, g.views
                    FROM c7_groups g, c7_groups_affiliations ga, c7_affiliations a
                    WHERE ga.affiliations_id = a.id
                        AND ga.groups_hash = g.hash
                        AND LOWER(a.name) LIKE LOWER('%$school_name%')";
) as myTbl
group by name

Answer 2

试试这个

SELECT Distinct 
           g.name, g.hash, g.views
                    FROM c7_groups g, c7_groups_affiliations ga
                    WHERE g.category >= 592 AND g.category <= 622
                        AND ga.affiliated_groups_hash = g.hash
                        AND LOWER(g.name) LIKE LOWER('%$school_name%')
UNION
SELECT 
           g.name, g.hash, g.views
                    FROM c7_groups g, c7_groups_affiliations ga, c7_affiliations a
                    WHERE ga.affiliations_id = a.id
                        AND ga.groups_hash = g.hash
                        AND LOWER(a.name) LIKE LOWER('%$school_name%')

Answer 3

似乎第一个查询和第二个查询之间的唯一区别是有一个连接。如果您使用 ANSI-92 连接，可能会是这样，并且不需要 UNION。

          SELECT DISTINCT 
                   g.name, 
                   g.hash,
                   g.views
            FROM 
                    c7_groups g
                  INNER JOIN  c7_groups_affiliations ga
                  ON ga.affiliated_groups_hash = g.hash
                  LEFT JOIN c7_affiliations a
                   on ga.affiliations_id = a.id

            WHERE 
                (LOWER(g.name) LIKE LOWER('%$school_name%')
                 AND g.category >= 592 AND g.category <= 622 
                 AND  a.ID is null)
                OR 
                 (LOWER(a.name) LIKE LOWER('%$school_name%')
                 and a.ID is NOT null)

从技术上讲，第二部分中的 a.ID is NOT null 不是必需的，因为 LOWER(a.name) LIKE LOWER('%$school_name%') 会这样做，但它可以更清楚地说明发生了什么