Order By in Postgres

Question

I want to get the result set in the descending range order. Below is my Query

select quantity_range as quantity_range, count(*) as number_of_items,
sum(amount) as total_amount,
from (
  select *,case
    when quantity between 0 and 500 then '<=500'
    when quantity between 501 and 525 then '501-525'
    when quantity between 526 and 550 then '526-550'
    when quantity between 551 and 575 then '551-575'
    when quantity between 576 and 600 then '576-600'
    when quantity between 601 and 625 then '601-625'
    when quantity between 626 and 650 then '626-650'
    when quantity between 651 and 675 then '651-675'
    when quantity between 676 and 700 then '676-700'
    when quantity between 701 and 725 then '701-725'
    when quantity between 726 and 750 then '726-750'
    else '>750' end as quantity_range
  from Sales )
group by quantity_range order by quantity_range;

I want my Result set like:

<=500   100 100000.00
600-625 10  5000.00
>700    25  25000.00

How to get this ordering? If i give Order By clause then >700 coming at 2nd position.

Answer 1

Use RIGHT to get last number from string:

select quantity_range as quantity_range, count(*) as number_of_items,
sum(amount) as total_amount
from (
  select *,case
    when quantity between 0 and 500 then '<=500'
    when quantity between 501 and 525 then '501-525'
    when quantity between 526 and 550 then '526-550'
    when quantity between 551 and 575 then '551-575'
    when quantity between 576 and 600 then '576-600'
    when quantity between 601 and 625 then '601-625'
    when quantity between 626 and 650 then '626-650'
    when quantity between 651 and 675 then '651-675'
    when quantity between 676 and 700 then '676-700'
    when quantity between 701 and 725 then '701-725'
    when quantity between 726 and 750 then '726-750'
    else '>750' end as quantity_range
  from Sales ) as sub
group by quantity_range 
order by RIGHT(quantity_range,3);

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