postgresql：自加入数组

Question

我的问题是关于为以下用例

形成 Postgres SQL 查询

方法#1

我有一个如下所示的 table，我在不同类型（a、b、c、d）之间生成相同的 uuid，比如映射不同的类型。

+----+------+-------------+
| id | type | master_guid |
+----+------+-------------+
|  1 | a    | uuid-1      |
|  2 | a    | uuid-2      |
|  3 | a    | uuid-3      |
|  4 | a    | uuid-4      |
|  5 | a    | uuid-5      |
|  6 | b    | uuid-1      |
|  7 | b    | uuid-2      |
|  8 | b    | uuid-3      |
|  9 | b    | uuid-6      |
| 10 | c    | uuid-1      |
| 11 | c    | uuid-2      |
| 12 | c    | uuid-3      |
| 13 | c    | uuid-6      |
| 14 | c    | uuid-7      |
| 15 | d    | uuid-6      |
| 16 | d    | uuid-2      |
+----+------+-------------+

方法#2

我创建了两个 tables 供 id 键入，然后 id 为 master_guid，如下所示

table1:

+----+------+
| id | type |
+----+------+
|  1 | a    |
|  2 | a    |
|  3 | a    |
|  4 | a    |
|  5 | a    |
|  6 | b    |
|  7 | b    |
|  8 | b    |
|  9 | b    |
| 10 | c    |
| 11 | c    |
| 12 | c    |
| 13 | c    |
| 14 | c    |
| 15 | d    |
| 16 | d    |
+----+------+

table2

+----+-------------+
| id | master_guid |
+----+-------------+
|  1 | uuid-1      |
|  2 | uuid-2      |
|  3 | uuid-3      |
|  4 | uuid-4      |
|  5 | uuid-5      |
|  6 | uuid-1      |
|  7 | uuid-2      |
|  8 | uuid-3      |
|  9 | uuid-6      |
| 10 | uuid-1      |
| 11 | uuid-2      |
| 12 | uuid-3      |
| 13 | uuid-6      |
| 14 | uuid-7      |
| 15 | uuid-6      |
| 16 | uuid-2      |
+----+-------------+

我想通过两种方法获得如下输出：

+----+------+--------+------------+
| id | type |  uuid  | mapped_ids |
+----+------+--------+------------+
|  1 | a    | uuid-1 | [6,10]     |
|  2 | a    | uuid-2 | [7,11]     |
|  3 | a    | uuid-3 | [8,12]     |
|  4 | a    | uuid-4 | null       |
|  5 | a    | uuid-5 | null       |
+----+------+--------+------------+

我已尝试使用 array_agg 对 ID 进行自连接并基于 uuid 进行分组，但无法获得所需的输出。

使用以下查询填充数据：

方法#1

insert into table1 values 
(1,'a','uuid-1'),
(2,'a','uuid-2'),
(3,'a','uuid-3'),
(4,'a','uuid-4'),
(5,'a','uuid-5'),
(6,'b','uuid-1'),
(7,'b','uuid-2'),
(8,'b','uuid-3'),
(9,'b','uuid-6'),
(10,'c','uuid-1'),
(11,'c','uuid-2'),
(12,'c','uuid-3'),
(13,'c','uuid-6'),
(14,'c','uuid-7'),
(15,'d','uuid-6'),
(16,'d','uuid-2')

方法#2

insert into table1 values 
(1,'a'),
(2,'a'),
(3,'a'),
(4,'a'),
(5,'a'),
(6,'b'),
(7,'b'),
(8,'b'),
(9,'b'),
(10,'c'),
(11,'c'),
(12,'c'),
(13,'c'),
(14,'c'),
(15,'d'),
(16,'d')

insert into table2 values 
(1,'uuid-1'),
(2,'uuid-2'),
(3,'uuid-3'),
(4,'uuid-4'),
(5,'uuid-5'),
(6,'uuid-1'),
(7,'uuid-2'),
(8,'uuid-3'),
(9,'uuid-6'),
(10,'uuid-1'),
(11,'uuid-2'),
(12,'uuid-3'),
(13,'uuid-6'),
(14,'uuid-7'),
(15,'uuid-6'),
(16,'uuid-2')

Answer 1

demo: db<>fiddle

使用 window function ARRAY_AGG 允许您汇总每个组的 id（在您的情况下，这些组是您的 uuid）

SELECT 
    id, type, master_guid as uuid, 
    array_agg(id) OVER (PARTITION BY master_guid) as mapped_ids
FROM table1
ORDER BY id

结果：

| id | type |   uuid | mapped_ids |
|----|------|--------|------------|
|  1 |    a | uuid-1 |     10,6,1 |
|  2 |    a | uuid-2 |  16,2,7,11 |
|  3 |    a | uuid-3 |     8,3,12 |
|  4 |    a | uuid-4 |          4 |
|  5 |    a | uuid-5 |          5 |
|  6 |    b | uuid-1 |     10,6,1 |
|  7 |    b | uuid-2 |  16,2,7,11 |
|  8 |    b | uuid-3 |     8,3,12 |
|  9 |    b | uuid-6 |    15,13,9 |
| 10 |    c | uuid-1 |     10,6,1 |
| 11 |    c | uuid-2 |  16,2,7,11 |
| 12 |    c | uuid-3 |     8,3,12 |
| 13 |    c | uuid-6 |    15,13,9 |
| 14 |    c | uuid-7 |         14 |
| 15 |    d | uuid-6 |    15,13,9 |
| 16 |    d | uuid-2 |  16,2,7,11 |

这些数组当前还包含当前行的 ID（id = 1 的 mapped_ids 包含 1）。这可以通过使用 array_remove:

删除此元素来纠正

SELECT 
    id, type, master_guid as uuid,  
    array_remove(array_agg(id) OVER (PARTITION BY master_guid), id) as mapped_ids
FROM table1
ORDER BY id

结果：

| id | type |   uuid | mapped_ids |
|----|------|--------|------------|
|  1 |    a | uuid-1 |       10,6 |
|  2 |    a | uuid-2 |    16,7,11 |
|  3 |    a | uuid-3 |       8,12 |
|  4 |    a | uuid-4 |            |
|  5 |    a | uuid-5 |            |
|  6 |    b | uuid-1 |       10,1 |
|  7 |    b | uuid-2 |    16,2,11 |
|  8 |    b | uuid-3 |       3,12 |
|  9 |    b | uuid-6 |      15,13 |
| 10 |    c | uuid-1 |        6,1 |
| 11 |    c | uuid-2 |     16,2,7 |
| 12 |    c | uuid-3 |        8,3 |
| 13 |    c | uuid-6 |       15,9 |
| 14 |    c | uuid-7 |            |
| 15 |    d | uuid-6 |       13,9 |
| 16 |    d | uuid-2 |     2,7,11 |

现在，例如 id=4 包含一个空数组而不是 NULL 值。这可以通过使用 NULLIF 函数来实现。如果两个参数相等，则给出 NULL，否则给出第一个参数。

SELECT 
    id, type, master_guid as uuid,  
    NULLIF(
        array_remove(array_agg(id) OVER (PARTITION BY master_guid), id), 
        '{}'::int[]
    ) as mapped_ids 
FROM table1
ORDER BY id

结果：

| id | type |   uuid | mapped_ids |
|----|------|--------|------------|
|  1 |    a | uuid-1 |       10,6 |
|  2 |    a | uuid-2 |    16,7,11 |
|  3 |    a | uuid-3 |       8,12 |
|  4 |    a | uuid-4 |     (null) |
|  5 |    a | uuid-5 |     (null) |
|  6 |    b | uuid-1 |       10,1 |
|  7 |    b | uuid-2 |    16,2,11 |
|  8 |    b | uuid-3 |       3,12 |
|  9 |    b | uuid-6 |      15,13 |
| 10 |    c | uuid-1 |        6,1 |
| 11 |    c | uuid-2 |     16,2,7 |
| 12 |    c | uuid-3 |        8,3 |
| 13 |    c | uuid-6 |       15,9 |
| 14 |    c | uuid-7 |     (null) |
| 15 |    d | uuid-6 |       13,9 |
| 16 |    d | uuid-2 |     2,7,11 |

Answer 2

试试这个：

select
  t1.id, t1.type, t1.master_guid, array_agg (distinct t2.id)
from
  table1 t1
  left join table1 t2 on
    t1.master_guid = t2.master_guid and
    t1.id != t2.id
group by
  t1.id, t1.type, t1.master_guid

我没有得出与您列出的完全相同的结果，但我认为这已经足够接近了，也许您的预期有误，或者我的只是一个小错误……无论哪种方式，一个潜在起点。

-- 编辑--

对于方法 #2，我认为您只需向 Table2 添加一个内部联接即可获取 GUID：

select
  t1.id, t1.type, t2.master_guid,
  array_agg (t2a.id)
from
  table1 t1
  join table2 t2 on t1.id = t2.id
  left join table2 t2a on
    t2.master_guid = t2a.master_guid and
    t2a.id != t1.id
where
  t1.type = 'a'
group by
  t1.id, t1.type, t2.master_guid

postgresql：自加入数组

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