Question

我的PostgreSQL数据库中有3个表，实现了多对多关系：droit，role和role_droit。请参见附图中的图表。我有这个查询来返回当前结果（也在图像中）：

SELECT matrix_view.droit_id,
    sum(case when matrix_view.aid = 1 then haspair end) as  "role A" ,
    sum(case when matrix_view.aid = 2 then haspair end) as  "role B" ,
    sum(case when matrix_view.aid = 3 then haspair end) as  "role C" ,
    sum(case when matrix_view.aid = 4 then haspair end) as  "role D"
from (
        SELECT allRD.aid as aid, allRD.droit_id, max(case when RD.role_id is not null then 1 else 0 end) as HasPair
        from (
                select distinct a.role_id as aid, b.droit_id as droit_id
                from role a cross join droit b 
             ) as allRD 
        left outer join role_Droit RD
        on allRD.aid = RD.role_id and allRD.droit_id = RD.droit_id
        group by  allRD.droit_id,  allRD.aid
        order by  allRD.aid
    ) AS matrix_view
group by matrix_view.droit_id
order by matrix_view.droit_id

我想在id_droit和id_role的交集中显示haspair，droit和role的串联！ 所需结果也位于图片中：

Answer 1

请注意：您在查询中使用固定数字（"role A" , "role B" , "role C" , "role D"），我也使用它们。

尝试以下查询：

SELECT cast(matrix_view.droit_name as text),
    matrix_view.droit_id || ',' || sum(case when matrix_view.aid = 1 then matrix_view.aid end) || ',' || sum(case when matrix_view.aid = 1 then haspair end) as  "role A" ,
    matrix_view.droit_id || ',' || sum(case when matrix_view.aid = 2 then matrix_view.aid end) || ',' || sum(case when matrix_view.aid = 2 then haspair end) as  "role B" ,
    matrix_view.droit_id || ',' || sum(case when matrix_view.aid = 3 then matrix_view.aid end) || ',' || sum(case when matrix_view.aid = 3 then haspair end) as  "role C" ,
    matrix_view.droit_id || ',' || sum(case when matrix_view.aid = 4 then matrix_view.aid end) || ',' || sum(case when matrix_view.aid = 4 then haspair end) as  "role D"

from (
        SELECT allRD.aid as aid, allRD.droit_id,allRD.droit_name , max(case when RD.role_id is not null then 1 else 0 end) as HasPair
        from (
                select distinct a.role_id as aid, b.droit_id as droit_id , b.droit_name as droit_name
                from role a cross join droit b 
             ) as allRD 
        left outer join role_Droit RD
        on allRD.aid = RD.role_id and allRD.droit_id = RD.droit_id
        group by  allRD.droit_id,  allRD.aid ,allRD.droit_name
        order by  allRD.aid
    ) AS matrix_view
group by matrix_view.droit_id, matrix_view.droit_name
order by matrix_view.droit_id

Answer 2

通常，枢轴/交叉表问题。但是，由于您希望获得一小组给定角色的结果，我们可以采用一种捷径：

SELECT droit_name
     , droit_id || ',1,' || EXISTS (SELECT FROM role_droit WHERE droit_id = d.droit_id AND role_id = 1)::int AS "role A"
     , droit_id || ',2,' || EXISTS (SELECT FROM role_droit WHERE droit_id = d.droit_id AND role_id = 2)::int AS "role B"
     , droit_id || ',3,' || EXISTS (SELECT FROM role_droit WHERE droit_id = d.droit_id AND role_id = 3)::int AS "role C"
     , droit_id || ',4,' || EXISTS (SELECT FROM role_droit WHERE droit_id = d.droit_id AND role_id = 4)::int AS "role D"
FROM   droit d
ORDER  BY droit_id;

准确地产生您想要的结果。

我手动提供了角色名称和ID，因为您只需要给定角色的结果，并且无论如何都无法在SQL中动态更改列的数量和名称。

dbfiddle here

从两个表连接矩阵的字符串

2 个答案: