问题
I've a table that looks like:
id | user_id | activity_id | activity_type | root_id | is_root | timestamp
----+---------+-------------+---------------+---------+---------+-----------
1 | 1 | 1 | text | 1 | 1 | 5
2 | 2 | 2 | text | 1 | 0 | 6
3 | 3 | 3 | text | 1 | 0 | 10
4 | 2 | 10 | text | 10 | 1 | 50
5 | 1 | 11 | text | 10 | 0 | 90
6 | 3 | 12 | text | 10 | 0 | 100
7 | 3 | 20 | text | 20 | 1 | 190
8 | 2 | 21 | text | 20 | 0 | 130
9 | 3 | 22 | text | 20 | 0 | 150
10 | 3 | 22 | text | 20 | 0 | 150
11 | 3 | 22 | text | 20 | 0 | 150
I want an out put like
id | user_id | activity_id | activity_type | root_id | is_root | timestamp
----+---------+-------------+---------------+---------+---------+-----------
7 | 3 | 20 | text | 20 | 1 | 120
8 | 2 | 21 | text | 20 | 0 | 130
11 | 3 | 22 | text | 20 | 0 | 150
9 | 3 | 22 | text | 20 | 0 | 150
10 | 3 | 22 | text | 20 | 0 | 150
4 | 2 | 10 | text | 10 | 1 | 50
5 | 1 | 11 | text | 10 | 0 | 90
6 | 3 | 12 | text | 10 | 0 | 100
1 | 1 | 1 | text | 1 | 1 | 5
2 | 2 | 2 | text | 1 | 0 | 6
3 | 3 | 3 | text | 1 | 0 | 10
The root_id should be placed in one group, and the first row of that group should have is_root = 1. The groups should be sorted on the basis of timestamp of root DESC, but the children of the root should be sorted ASC (timestamp based)
The relevant columns for the question is root_id, is_root, timestamp.
Any help is appreciated.
Thanks
回答1:
Are you talking about this?
ORDER BY root_id DESC, is_root DESC, timestamp
回答2:
order by root_id desc, is_root desc, timestamp asc
should do the trick.
来源：https://stackoverflow.com/questions/6629785/postgresql-ordered-result