Question

我不确定Postgres是否可行，但我希望每一行都能计算其窗函数＆＃34; frame＆＃34;。

那么如何在Postgres的窗口函数中使用当前行中的列作为JobScheduler的参数？

例如..

ROWS

我想使用create table items ( id serial primary key, name varchar, price integer, precede_by integer ); insert into items (name, price, precede_by) values ('A', 1, 2), ('A', 1, 3), ('B', 1, 1),('B',1, 2), ('B', 1, 1), ('B', 2, 2), ('C', 1, 2), ('C', 1,2), ('C', 1, 2), ('C', 1, 5);列中设置的整数值..例如，像这样..

precede_by

但这不起作用。我收到了select name, sum(price) over (partition by name rows between precede_by preceding and current row) from items;

Answer 1

不，无法根据需要编写窗口功能。我相信CROSS JOIN LATERAL可以做到这一点

with oitems as
(
  select *, row_number() over (partition by name order by id) rn from items
)
select * 
from oitems i1
cross join lateral 
(
  select sum(price) 
  from  oitems i2
  where i1.name = i2.name and i2.rn >= i1.rn - i1.precede_by and i2.rn <= i1.rn
) t

和另一个（可能更优雅）的解决方案就是使用GROUP BY

进行自我加入

with oitems as
(
  select *, row_number() over (partition by name order by id) rn from items
)
select i1.id, i1.name, i1.price, sum(i2.price) 
from oitems i1
join  oitems i2 on i1.name = i2.name and i2.rn >= i1.rn - i1.precede_by and i2.rn <= i1.rn
group by i1.id, i1.name, i1.price

dbfiddle demo

如何在Postgres动态帧中使用窗口函数中的列值？

1 个答案: