更新: https://www.db-fiddle.com/f/5fGUTSsAhGRPYPk33wDSzz/0
很抱歉提出了与上一个问题非常相似的问题,但我真的被困在这里了。
有多个表:
- 项目 → items_roles → 角色
- 项目 → 区域 → roles_zones → 角色
结构:
- 项目:id,zone_id
- items_roles: role_id, item_id
- 区域:id
- roles_zones: role_id, zone_id
- 角色:id,role_type_id,
我正在尝试向项目添加角色字段,它应该采用 role_type 并且它是来自 items_zones 的值,如果它是 NULL,则从区域 (roles_zones) 获取回退值。
我开始于:
SELECT
items.id,
(z_roles.role_type_id) as z_role_type_id,
(z_roles.id) as z_role_id,
MAX(i_roles.role_type_id) as i_role_type_id,
MAX(i_roles.id) as i_role_id
FROM
items
LEFT JOIN
zones as j_zones ON j_zones.id = items.zone_id
LEFT JOIN
roles_zones ON roles_zones.zone_id = j_zones.id
LEFT JOIN
roles as z_roles ON (z_roles.id = roles_zones.role_id)
LEFT JOIN
items_roles ON items_roles.item_id = items.id
LEFT JOIN
roles as i_roles ON items_roles.role_id = i_roles.id
AND (z_roles.role_type_id = i_roles.role_type_id)
WHERE
items.id = 834
GROUP BY
items.id, z_roles.role_type_id, z_roles.id
ORDER BY
i_role_id;
看起来不错:
id |z_role_type_id |z_role_id |i_role_type_id |i_role_id |
----+---------------+----------+---------------+----------+
834 |5 |111 |5 |68 |
834 |11 |120 |11 |120 |
834 |7 |77 | | |
834 |2 |2 | | |
834 |12 |91 | | |
834 |4 |78 | | |
834 |8 |36 | | |
现在这个查询:
SELECT
items.id,
z_roles.role_type_id as z_role_type_id,
z_roles.id as z_role_id,
MAX(i_roles.role_type_id) AS i_role_type_id,
MAX(i_roles.id) AS i_role_id,
MAX(CASE
WHEN (i_roles.role_type_id = 5) THEN i_roles.id
WHEN (z_roles.role_type_id = 5) THEN z_roles.id
END) AS role_type_5_value,
MAX(CASE
WHEN (i_roles.role_type_id = 11) THEN i_roles.id
WHEN (z_roles.role_type_id = 11) THEN z_roles.id
END) AS role_type_11_value,
MAX(CASE
WHEN (i_roles.role_type_id = 7) THEN i_roles.id
WHEN (z_roles.role_type_id = 7) THEN z_roles.id
END) AS role_type_7_value
FROM
items
LEFT JOIN
zones AS j_zones ON j_zones.id = items.zone_id
LEFT JOIN
roles_zones ON roles_zones.zone_id = j_zones.id
LEFT JOIN
roles AS z_roles ON (z_roles.id = roles_zones.role_id)
LEFT JOIN
items_roles ON items_roles.item_id = items.id
LEFT JOIN
roles AS i_roles ON items_roles.role_id = i_roles.id
AND (z_roles.role_type_id = i_roles.role_type_id)
WHERE
items.id = 834
GROUP BY
items.id,
z_roles.role_type_id,
z_roles.id
ORDER BY
items.id, i_role_id;
生成这个:
id | z_role_type_id | z_role_id | i_role_type_id | i_role_id | role_type_5_value | role_type_11_value | role_type_7_value
-----+----------------+-----------+----------------+-----------+-------------------+--------------------+-------------------
834 | 5 | 111 | 5 | 68 | 111 | |
834 | 11 | 120 | 11 | 120 | | 120 |
834 | 7 | 77 | | | | | 77
834 | 2 | 2 | | | | |
834 | 12 | 91 | | | | |
834 | 4 | 78 | | | | |
834 | 8 | 36 | | | | |
(7 rows)
role_type_5_value
有多行且值错误。可能是因为 MAX 聚合器。是否可以使用类似 first
聚合器的东西(因为按 i_role_id 排序的行和第一个结果是正确的)?
我想要这个:
id | role_type_5_value | role_type_11_value | role_type_7_value
-----+-------------------+--------------------+-------------------
834 | 68 | 120 | 77
我试图通过聚合字段分组依据
,(role_type_5_value
, role_type_11_value
, role_type_7_value
) 但这是根本不起作用。
最佳答案
首先:从主查询中删除不需要的桥接表并将它们压缩到 EXISTS()
项中将简化您的查询。(您只需要三个表,其余的是胶水)
其次:不要将所有术语都放在 GROUP BY
子句中。
SELECT
i0.id
, MAX(CASE
WHEN (r1.role_type_id = 5) THEN r1.id
WHEN (r0.role_type_id = 5) THEN r0.id
END) AS role_type_5_value
, MAX(CASE
WHEN (r1.role_type_id = 11) THEN r1.id
WHEN (r0.role_type_id = 11) THEN r0.id
END) AS role_type_11_value
, MAX(CASE
WHEN (r1.role_type_id = 7) THEN r1.id
WHEN (r0.role_type_id = 7) THEN r0.id
END) AS role_type_7_value
FROM items i0
LEFT JOIN roles AS r0
ON EXISTS ( SELECT*
FROM zones AS z0
JOIN roles_zones rz ON rz.zone_id = z0.id
WHERE z0.id = i0.zone_id
AND r0.id = rz.role_id)
LEFT JOIN roles AS r1
ON EXISTS ( SELECT*
FROM items_roles ir
WHERE ir.item_id = i0.id
AND ir.role_id = r1.id
AND r0.role_type_id = r1.role_type_id
)
WHERE i0.id = 834
GROUP BY i0.id
-- r0.role_type_id,
-- r0.id
ORDER BY i0.id;
关于sql - group by 后将多行合并为一行,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/50420624/