伯爵在Table2_arrays

Question

Table1_IDs我有兩個表的工作：

CREATE TABLE Table1 
(
id int, 
name varchar 
) 

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

Table2.link包含對應Table1.id值。我想統計每個Table1.id出現在Table2.link的實例中的次數。這在Excel中使用單元格引用很簡單，但我無法弄清楚如何使用SQL查詢來完成它。

Answer 1

普雷斯托

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的演示

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 | 
+----+-----+