aggregated functions and group by postgresql

[obi]

We need to remove the median sample and sample size. the median is the value of which порядковому номеру = размер/2 rounded down to the lower side,

i.e. this example should be 33 in place 7

We need to sign 33/15.

Here's my code, which doesn't work like this the use of aggregate functions requires a group by

CREATE TABLE random(ID INT primary key , Value INT unique )  
INSERT INTO random 
values 
(1,1),
(2,3),
(3,7),
(4,10),
(5,16),
(6,17),
(7,33),
(8,21),
(9,27),
(10,41),
(11,25),
(12,13),
(13,23),
(14,29),
(15,9)
Select  cast count() as tatal, value  from random

where  id =  cast (count()/2 as int)

Is it possible to rewrite something with help? group by ? free with as и limit

[Pearlaqua]

Try using the sub-conquests:

SELECT
    (select count(*) from random) as total_count,
    value 
FROM

random

WHERE

id = (select cast (count()/2 as int) from random)

UPD.

Then instead id row number

SELECT tcount, value FROM

(SELECT

ROW_NUMBER() over (ORDER BY id) as rnum,

COUNT() over () as tcount,

value

FROM random) sq

WHERE

sq.rnum = (select cast (count(*)/2 as int) from random)