Postgres grouping by range

Question

I have data looking like this

What I am trying to achieve is data for historgram that would count values into specific ranges. For category A value range 1-100 and for category B value range 0-125 where value for category C = 5. The problem I have that is data in multiplerows and I need to filter first on C and then count values into ranges to display histogram. To get counts lets say per 10 seconds looking like this

Code to generate data:

CREATE TEMP TABLE sample (
     ts timestamp
    ,category varchar(2)
    , val int)
    
insert into sample values 
(to_timestamp('01.01.2018 08:00:01', 'dd-mm-yyyy hh24:mi:ss'), 'A', 12),
(to_timestamp('01.01.2018 08:00:02', 'dd-mm-yyyy hh24:mi:ss'), 'A', 44),
(to_timestamp('01.01.2018 08:00:03', 'dd-mm-yyyy hh24:mi:ss'), 'C', 1),
(to_timestamp('01.01.2018 08:00:04', 'dd-mm-yyyy hh24:mi:ss'), 'B', 24),
(to_timestamp('01.01.2018 08:00:05', 'dd-mm-yyyy hh24:mi:ss'), 'B', 111),
(to_timestamp('01.01.2018 08:00:06', 'dd-mm-yyyy hh24:mi:ss'), 'C', 5),
(to_timestamp('01.01.2018 08:00:07', 'dd-mm-yyyy hh24:mi:ss'), 'A', 145),
(to_timestamp('01.01.2018 08:00:01', 'dd-mm-yyyy hh24:mi:ss'), 'B', 16),
(to_timestamp('01.01.2018 08:00:01', 'dd-mm-yyyy hh24:mi:ss'), 'C', 47),
(to_timestamp('01.01.2018 08:00:02', 'dd-mm-yyyy hh24:mi:ss'), 'C', 5),
(to_timestamp('01.01.2018 08:00:02', 'dd-mm-yyyy hh24:mi:ss'), 'B', 34),
(to_timestamp('01.01.2018 08:00:03', 'dd-mm-yyyy hh24:mi:ss'), 'B', 111),
(to_timestamp('01.01.2018 08:00:03', 'dd-mm-yyyy hh24:mi:ss'), 'C', 5),
(to_timestamp('01.01.2018 08:00:01', 'dd-mm-yyyy hh24:mi:ss'), 'A', 19),
(to_timestamp('01.01.2018 08:00:01', 'dd-mm-yyyy hh24:mi:ss'), 'B', 46),
(to_timestamp('01.01.2018 08:00:01', 'dd-mm-yyyy hh24:mi:ss'), 'C', 57)

I thought if I pivot data like so

s

elect 
    ts, 
    category,
    case when category = 'A' then val end as "A",
    case when category = 'B' then val end as "B",
    case when category = 'C' then val end as "C"
from sample
order by ts

then have problem with pivot nulls

Answer 1

Here it is:

with periods(pts) as 
(
 select * 
 from generate_series
 (
   timestamp '2018-01-01 08:00:00', 
   timestamp '2018-01-01 08:01:00', 
   interval '10 seconds'
 ) ts
)
select  pts period_start, 
        pts + interval '10 seconds' period_end,
        lat.cat_a, 
        lat.cat_b, 
        lat.cat_c
from periods 
cross join lateral 
(
 select  count(1) filter (where category = 'A' and val between 0 and 100) as cat_a, 
         count(1) filter (where category = 'B' and val between 0 and 125) as cat_b, 
         count(1) filter (where category = 'C' and val = 5) as cat_c
 from sample 
 where ts >= pts and ts < pts + interval '10 seconds'
) lat; 

period_start	period_end	cat_a	cat_b	cat_c
2018-01-01 08:00:00	2018-01-01 08:00:10	2	2	1
2018-01-01 08:00:10	2018-01-01 08:00:20	0	0	0
2018-01-01 08:00:20	2018-01-01 08:00:30	0	0	0
2018-01-01 08:00:30	2018-01-01 08:00:40	0	0	0
2018-01-01 08:00:40	2018-01-01 08:00:50	0	0	0
2018-01-01 08:00:50	2018-01-01 08:01:00	0	0	0
2018-01-01 08:01:00	2018-01-01 08:01:10	0	0	0

One-row version is simple:

select  min(ts) period_start,
        max(ts) period_end,
        count(1) filter (where category = 'A' and val between 0 and 100) as cat_a, 
        count(1) filter (where category = 'B' and val between 0 and 125) as cat_b, 
        count(1) filter (where category = 'C' and val = 5) as cat_c
from sample; 

Added after the clarification comments

select * from (<the first version of the query here>) t where cat_c > 0;