我有一组表格,用于描述人们的位置流量。主要的'travel_flows'表格具有如下表中所示的结构。流的顺序由'order_id'列描述。
+-----------+------------+---------+-------------+----------+ | travel_id | purpose_id | name_id | location_id | order_id | +-----------+------------+---------+-------------+----------+ | 434 | 23 | 55 | 85 | 1 | | 212 | 43 | 55 | 45 | 2 | | 411 | 41 | 55 | 17 | 3 | | 148 | 23 | 32 | 32 | 1 | | 153 | 11 | 32 | 19 | 2 | +-----------+------------+---------+-------------+----------+
我想用PostgreSQL 9.6实现的目的是根据'location_id'和'order_id'值以二进制原点(from)/ destination(to)格式将返回的行按'name_id'分组,类似于以下内容表:
+-----------------+--------------+------------------+---------------+------------+----------------+ | from_purpose_id | from_name_id | from_location_id | to_purpose_id | to_name_id | to_location_id | +-----------------+--------------+------------------+---------------+------------+----------------+ | 23 | 55 | 85 | 43 | 55 | 45 | | 43 | 55 | 45 | 41 | 55 | 17 | | 23 | 32 | 32 | 11 | 32 | 19 | +-----------------+--------------+------------------+---------------+------------+----------------+
有没有办法用select语句实现这个目的?
答案 0 :(得分:2)
您可以使用lead
窗口功能执行此操作。
select * from (
select purpose_id,name_id,location_id,
lead(purpose_id) over(partition by name_id order by order_id) as to_purpose_id,
lead(name_id) over(partition by name_id order by order_id) as to_name_id,
lead(location_id) over(partition by name_id order by order_id) as to_location_id
from tbl
) t
where to_purpose_id is not null and to_name_id is not null and to_location_id is not null
答案 1 :(得分:1)
您可以使用窗口函数轻松实现此目的(请参阅https://www.postgresql.org/docs/current/static/tutorial-window.html),特别是函数lead()
:
with flow as (
select
name_id,
purpose_id as from_purpose_id,
lead(purpose_id) over w1 as next_purpose_id,
location_id as from_location_id,
lead(location_id) over w1 as next_location_id,
order_id
from travel_flows
window w1 as (partition by name_id order by order_id)
)
select
name_id, from_purpose_id, next_purpose_id, from_location_id, next_location_id
from flow
where next_purpose_id is not null
order by name_id, order_id
;