PostgreSQL按日期排序但随机

Question

I'm trying to pull data and arrange it by date but have it appear in a random order. I've tried

SELECT * FROM table ORDER BY article_date_added::DATE DESC, RANDOM() limit 30;

And I've tried

SELECT * FROM table ORDER BY to_timestamp(to_char(article_date_added, \'DD Mon YYYY HH24\'), \'DD Mon YYYY\') DESC, RANDOM()

It gets the most recent articles but then it make it random by the day. So it will be like

April 1
March 29
March 31
Apr 1

I'm trying to acheive results seperated by the date but then made random.

April 1
April 1
March 31
March29

Is there a way I can do this in SQL?

Answer 1

Put the part where you get the 30 most recent articles into a subquery and select from the subquery ordering by random. I don't use postgresql so this example may have some errors:

select * from 
(select somefields
from sometables
order by article_date_added desc
limit 30) temp
order by random()

Answer 2

So, you want every day grouped together but the dates presented in a random order, right? We can use the built-in function generate_series which can take timestamp arguments to make a pseudo-table that can help.

WITH t AS (
  SELECT gs::date AS dt, random() AS r 
  FROM generate_series('2010-01-01'::timestamp, '2015-01-01', '1 day') AS gs )
SELECT articles.* 
FROM articles JOIN t 
ON articles.article_date_added::date=t.dt 
ORDER BY r;

Note that it isn't necessary to have r in the output columns.

Obviously this code will only work for another 2 years 9 months, but necessary modifications should be obvious. You can even replace the hardwired dates with (SELECT min(article_date_added) FROM articles) [note extra parentheses!] and likewise for max .

---

[Edit after comments] In looking over your sample output, I see you don't want aggregation by date. I'm not sure the description matches the output. What you are asking for is probably in one of the other suggestions, but you can do it easily with

WITH t AS (
  SELECT * FROM articles
  ORDER BY article_created_date DESC LIMIT 30 )
SELECT * FROM t ORDER BY t.article_created_date desc, random();

Answer 3

I think the following will work:

select t.*
from (select t.*,
             avg(random()) over (partition by article_date_added::DATE) as groupnum
      from t
     ) t
order by groupnum;

Or, if you want the dates descending and then random do:

select t.*
from t
order by article_date_added::DATE desc, random();

This is how your example data is structured.

Answer 4

select DATE
from TABLE 
order by date_trunc('month',DATE),
random()

This works by first truncating the date into the month and sorting it. So, 2012-01-25 and 2012-01-13 become 2012-01-01.

After that, sort the actual date randomly.