Graf von Table1_IDs in Table2_arrays

Question

Ich arbeite mit zwei Tabellen:

CREATE TABLE Table1 
(
id int, 
name varchar 
) 

CREATE TABLE Table2 
(
id int, 
name varchar, 
link array<int> 
) 

Table2.link enthält Werte, die zu Table1.id entsprechen. Ich würde gerne zählen, wie oft jede Table1.id in einer Instanz von Table2.link erscheint. Dies wäre trivial mit Zellverweisen in Excel, aber ich kann nicht herausfinden, wie man es mit einer SQL-Abfrage macht.

Answer 1

Presto

select * 
from  (select l.id   
        ,count(*) as cnt 
      from  Table2 cross join unnest (link) as l(id) 
      group by l.id  
     ) t2 
where  t2.id in (select id from Table1) 
order by id 

---

presto:default> select * 
      -> from  (select l.id 
      ->     ,count(*) as cnt 
      ->   from  Table2 cross join unnest (link) as l(id) 
      ->   group by l.id 
      ->   ) t2 
      -> where  t2.id in (select id from Table1) 
      -> order by id; 
id | cnt 
----+----- 
    1 | 7 
    2 | 5 
    3 | 4 
(3 rows) 

PostgreSQL Demo

create table Table1 (id int); 
create table Table2 (arr int[]); 

insert into Table1 values 
    (1),(2),(3) 
; 

insert into Table2 values 
    (array[1,5]),(array[1,3]),(array[1,2,3]),(array[2,3]) 
    ,(array[1,2,4]),(array[1,2]),(array[1,3,5]),(array[1,2,4]) 
; 

---

select * 
from  (select unnest(arr) as id    
        ,count(*) as cnt 
      from  Table2 
      group by id  
     ) t2 
where  t2.id in (select id from Table1) 
order by id 

---

+----+-----+ 
| id | cnt | 
+----+-----+ 
| 1 | 7 | 
+----+-----+ 
| 2 | 5 | 
+----+-----+ 
| 3 | 4 | 
+----+-----+