sql - Postgresql 选择计数与连接

Question

我有两个表:

CREATE TABLE stores (
stores_id varchar PRIMARY KEY,
owner_id varchar
);

CREATE TABLE sets (
sets_id varchar PRIMARY KEY,
stores_id varchar not null,
owner_id varchar not null,
item_id varchar not null,
);

我如何发出显示商店中套装商品数量的请求？由所有者选择。

例如:

select
stores.*,
count(sets.item_id)
from stores
LEFT OUTER JOIN sets on stores.owner_id = sets.owner_id
where
stores.owner_id = 'e185775fc4f5'
GROUP BY stores.owner_id;

谢谢。

Answer 1

我认为您需要加入商店和所有者，然后是 COUNT(DISTINCT item_id)

select
st.owner_id, 
st.stores_id, 
count(distinct se.item_id)
  from stores st left join
    sets se
       on st.owner_id = se.owner_id
       and st.stores_id = se.stores_id
           group by st.owner_id, st.stores_id;

这将给出一个表，其中显示所有者、商店，然后是商品数量