creating a pseudo linked list in sql

问题

I have a table that has the following columns

table: route
columns: id, location, order_id

and it has values such as

id, location, order_id
1, London, 12
2, Amsterdam, 102
3, Berlin, 90
5, Paris, 19

Is it possible to do a sql select statement in postgres that will return each row along with the id with the next highest order_id? So I want something like...

id, location, order_id, next_id
1, London, 12, 5
2, Amsterdam, 102, NULL
3, Berlin, 90, 2
5, Paris, 19, 3

Thanks

回答1:

select 
  id, 
  location, 
  order_id,
  lag(id) over (order by order_id desc) as next_id
from your_table

回答2:

Creating testbed first:

CREATE TABLE route (id int4, location varchar(20), order_id int4);
INSERT INTO route VALUES
    (1,'London',12),(2,'Amsterdam',102),
    (3,'Berlin',90),(5,'Paris',19);

The query:

WITH ranked AS (
    SELECT id,location,order_id,rank() OVER (ORDER BY order_id)
      FROM route)
SELECT b.id, b.location, b.order_id, n.id
  FROM ranked b
  LEFT JOIN ranked n ON b.rank+1=n.rank
  ORDER BY b.id;

You can read more on the window functions in the documentation.

回答3:

yes:

select * ,
(select top 1 id from routes_table where order_id > main.order_id order by 1 desc)
from routes_table main

来源：https://stackoverflow.com/questions/10348778/creating-a-pseudo-linked-list-in-sql