sql-generate-histogram.sql

-- db=# \d order_payment
--                    Table "public.order_payment"
--      Column       |            Type             | Collation | Nullable | Default
-- -----------------+-----------------------------+-----------+----------+---------
-- id                | uuid                        |           | not null |
-- order_id          | uuid                        |           |          |
-- amount_paid       | numeric                     |           |          |
-- ...

select
    bucket,
    range,
    freq,
    repeat('==', (freq::float /sum(freq) over() *30 )::int ) as bar
from (
    select
        width_bucket(amount_paid::int, 1, 10000, 20) as bucket,
        int4range(min(amount_paid::int), max(amount_paid::int), '[]') as range,
        count(*) as freq 
    from order_payment
    group by bucket
) as hist
order by freq desc

----
 bucket |     range     | freq |                             bar
--------+---------------+------+--------------------------------------------------------------
      1 | [1,501)       |   47 | ============================================================
      2 | [600,1001)    |   23 | ==============================
      3 | [1050,1501)   |   19 | ========================
      5 | [2050,2451)   |    7 | ========
      4 | [1600,2001)   |    7 | ========
      6 | [2600,3001)   |    5 | ======
      7 | [3168,3326)   |    4 | ======
     21 | [10000,64501) |    4 | ======
      8 | [3600,4001)   |    4 | ======
     14 | [6530,6531)   |    1 | ==
     11 | [5400,5401)   |    1 | ==
     10 | [4810,4811)   |    1 | ==
     15 | [7020,7021)   |    1 | ==
(13 rows)