问题
My table has account_id and device_id. One account_id could have multiple device_ids and vice versa. I am trying to count the depth of each connected many-to-many relationship.
Ex:
account_id | device_id
1 | 10
1 | 11
1 | 12
2 | 10
3 | 11
3 | 13
3 | 14
4 | 15
5 | 15
6 | 16
How do I construct a query that knows to combine accounts 1-3 together, 4-5 together, and leave 6 by itself? All 7 entries of accounts 1-3 should be grouped together because they all touched the same account_id or device_id at some point. I am trying to group them together and output the count.
Account 1 was used on device's 10, 11, 12. Those devices used other accounts too so we want to include them in the group. They used additional accounts 2 and 3. But account 3 was further used by 2 more devices so we will include them as well. The expansion of the group brings in any other account or device that also "touched" an account or device already in the group.
A diagram is shown below:
回答1:
You can use a recursive cte:
with recursive t(account_id, device_id) as (
select 1, 10 union all
select 1, 11 union all
select 1, 12 union all
select 2, 10 union all
select 3, 11 union all
select 3, 13 union all
select 3, 14 union all
select 4, 15 union all
select 5, 15 union all
select 6, 16
),
a as (
select distinct t.account_id as a, t2.account_id as a2
from t join
t t2
on t2.device_id = t.device_id and t.account_id >= t2.account_id
),
cte as (
select a.a, a.a2 as mina
from a
union all
select a.a, cte.a
from cte join
a
on a.a2 = cte.a and a.a > cte.a
)
select grp, array_agg(a)
from (select a, min(mina) as grp
from cte
group by a
) a
group by grp;
Here is a SQL Fiddle.
回答2:
You can GROUP BY the device_id and then aggregate together the account_id into a Postgres array. Here is an example query, although I'm not sure what your actual table name is.
SELECT
device_id,
array_agg(account_id) as account_ids
FROM account_device --or whatever your table name is
GROUP BY device_id;
Results - hope it's what you're looking for:
16 | {6}
15 | {4,5}
13 | {3}
11 | {1,3}
14 | {3}
12 | {1}
10 | {1,2}
回答3:
-- \i tmp.sql
CREATE TABLE graph(
account_id integer NOT NULL --references accounts(id)
, device_id integer not NULL --references(devices(id)
,PRIMARY KEY(account_id, device_id)
);
INSERT INTO graph (account_id, device_id)VALUES
(1,10) ,(1,11) ,(1,12)
,(2,10)
,(3,11) ,(3,13) ,(3,14)
,(4,15)
,(5,15)
,(6,16)
;
-- SELECT* FROM graph ;
-- Find the (3) group leaders
WITH seed AS (
SELECT row_number() OVER () AS cluster_id -- give them a number
, g.account_id
, g.device_id
FROM graph g
WHERE NOT EXISTS (SELECT*
FROM graph nx
WHERE (nx.account_id = g.account_id OR nx.device_id = g.device_id)
AND nx.ctid < g.ctid
)
)
-- SELECT * FROM seed;
;
WITH recursive omg AS (
--use the above CTE in a sub-CTE
WITH seed AS (
SELECT row_number()OVER () AS cluster_id
, g.account_id
, g.device_id
, g.ctid AS wtf --we need an (ordered!) canonical id for the tuples
-- ,just to identify and exclude them
FROM graph g
WHERE NOT EXISTS (SELECT*
FROM graph nx
WHERE (nx.account_id = g.account_id OR nx.device_id = g.device_id) AND nx.ctid < g.ctid
)
)
SELECT s.cluster_id
, s.account_id
, s.device_id
, s.wtf
FROM seed s
UNION ALL
SELECT o.cluster_id
, g.account_id
, g.device_id
, g.ctid AS wtf
FROM omg o
JOIN graph g ON (g.account_id = o.account_id OR g.device_id = o.device_id)
-- AND (g.account_id > o.account_id OR g.device_id > o.device_id)
AND g.ctid > o.wtf
-- we still need to exclude duplicates here
-- (which could occur if there are cycles in the graph)
-- , this could be done using an array
)
SELECT *
FROM omg
ORDER BY cluster_id, account_id,device_id
;
Results:
DROP SCHEMA
CREATE SCHEMA
SET
CREATE TABLE
INSERT 0 10
cluster_id | account_id | device_id
------------+------------+-----------
1 | 1 | 10
2 | 4 | 15
3 | 6 | 16
(3 rows)
cluster_id | account_id | device_id | wtf
------------+------------+-----------+--------
1 | 1 | 10 | (0,1)
1 | 1 | 11 | (0,2)
1 | 1 | 12 | (0,3)
1 | 1 | 12 | (0,3)
1 | 2 | 10 | (0,4)
1 | 3 | 11 | (0,5)
1 | 3 | 13 | (0,6)
1 | 3 | 14 | (0,7)
1 | 3 | 14 | (0,7)
2 | 4 | 15 | (0,8)
2 | 5 | 15 | (0,9)
3 | 6 | 16 | (0,10)
(12 rows)
Newer version (I added an Id column to the table)
-- for convenience :set of all adjacent nodes.
CREATE TEMP VIEW pair AS
SELECT one.id AS one
, two.id AS two
FROM graph one
JOIN graph two ON (one.account_id = two.account_id OR one.device_id = two.device_id)
AND one.id <> two.id
;
WITH RECURSIVE flood AS (
SELECT g.id, g.id AS parent_id
, 0 AS lev
, ARRAY[g.id]AS arr
FROM graph g
UNION ALL
SELECT c.id, p.parent_id AS parent_id
, 1+p.lev AS lev
, p.arr || ARRAY[c.id] AS arr
FROM graph c
JOIN flood p ON EXISTS (
SELECT * FROM pair WHERE p.id = pair.one AND c.id = pair.two)
AND p.parent_id < c.id
AND NOT p.arr @> ARRAY[c.id] -- avoid cycles/loops
)
SELECT g.*, a.parent_id
, dense_rank() over (ORDER by a.parent_id)AS group_id
FROM graph g
JOIN (SELECT id, MIN(parent_id) AS parent_id
FROM flood
GROUP BY id
) a
ON g.id = a.id
ORDER BY a.parent_id, g.id
;
New results:
CREATE VIEW
id | account_id | device_id | parent_id | group_id
----+------------+-----------+-----------+----------
1 | 1 | 10 | 1 | 1
2 | 1 | 11 | 1 | 1
3 | 1 | 12 | 1 | 1
4 | 2 | 10 | 1 | 1
5 | 3 | 11 | 1 | 1
6 | 3 | 13 | 1 | 1
7 | 3 | 14 | 1 | 1
8 | 4 | 15 | 8 | 2
9 | 5 | 15 | 8 | 2
10 | 6 | 16 | 10 | 3
(10 rows)
来源：https://stackoverflow.com/questions/45645335/how-to-count-all-the-connected-nodes-rows-in-a-graph-on-postgres