PostgreSQL Left Join with SUM 2 of 4 表

Question

我正在嘗試對 4 個表的 SUM 2 進行 LEFT JOIN，但我被卡住了

在下面底部的預期結果中， dates_stat的名為begin_stock和end_stock結果的新字段由daily_stock.qty過濾，但不需要使用sum() ，因為值是最終的。

您可以在這里嘗試： https://dbfiddle.uk/?rdbms=postgres_12&fiddle=07defd60df696a8717fc8e3096592545

繼承人的表：

product ：

id  product_name 
1   abc            
2   aaa            
3   bbb             
4   ddd             

usage ：需要使用 sum()

id  product_id  used    date_out
1   1           10      2020-12-18
2   1           20      2020-12-19
3   2           20      2020-12-18

product_restock ：需要使用 sum()

id  product_id  restock_amount  date_in
1   1           10              2020-12-18
2   1           20              2020-12-19
3   4           10              2020-12-19

daily_stock

id  product_id  qty dates_stat
1   1           10  2020-12-18
2   2           10  2020-12-18
3   3           10  2020-12-18
4   4           10  2020-12-18
5   1           10  2020-12-19
6   2           -10 2020-12-19
7   3           10  2020-12-19
8   4           20  2020-12-19

2020-12-18至2020-12-19的預期結果：

id      product_name  begin_stock   restock used end_stock
------  ------------  ------------- ------- ---- -------------
  1     abc           10            30      30   10
  2     aaa           10            0       20   -10 
  3     bbb           10            0       0    10    
  4     ddd           10            10      0    20

Answer 1

您可以使用聚合和橫向連接：

select p.*, ds.*, pr.*, u.*
from product p
cross join lateral (
    select 
        max(case when ds.date_stat = date '2020-12-18' then qty end) as begin_stock,
        max(case when ds.date_stat = date '2020-12-19' then qty end) as end_stock
    from daily_stock ds
    where 
        ds.product_id = p.id
        and ds.date_stat in (date '2020-12-18', date '2020-12-19')
) ds
cross join lateral (
    select coalesce(sum(u.used), 0) as used
    from usage u
    where 
        u.product_id = p.id 
        and u.date_out >= date '2020-12-18'
        and u.date_out <= date '2020-12-19'
) u
cross join lateral (
    select coalesce(sum(pr.restock_amount), 0) as restock
    from product_restock pr
    where 
        pr.product_id = p.id 
        and pr.date_in >= date '2020-12-18'
        and pr.date_in <= date '2020-12-19'     
) pr

DB Fiddle 上的演示：

 id | product_name | begin_stock | end_stock | restock | used
-: | :----------- | ----------: | --------: | ------: | ---:
 1 | abc          |          10 |        10 |      30 |   30
 2 | aaa          |          10 |       -10 |       0 |   20
 3 | bbb          |          10 |        10 |       0 |    0
 4 | ddd          |          10 |        20 |      10 |    0

Answer 2

    with start_end as
(
    select ds.product_id,ds.date_stat,ds.qty
    ,row_number() over(partition by ds.product_id order by ds.date_stat asc) start_dt
    ,row_number() over(partition by ds.product_id order by ds.date_stat desc) end_dt
    from daily_stock ds
)
,sum_of_restock_amount as
(
    select 
    pr.product_id ,sum(pr.restock_amount) restock
    from product_restock pr
    group by pr.product_id  
)
,sum_of_usage as
(
    select 
    u.product_id ,sum(u.used) used
    from usage u
    group by u.product_id
)
select pn.*,st.qty,res.restock,us.used,en.qty
from product  pn
left join start_end st
on pn.id = st.product_id
    and st.start_dt = 1
    and st.date_stat between '2020-12-18' and '2020-12-19'
left join sum_of_restock_amount res
on pn.id = res.product_id
left join sum_of_usage us
on pn.id = us.product_id
left join start_end en
on pn.id = en.product_id
    and en.end_dt = 1
    and en.date_stat between '2020-12-18' and '2020-12-19'