sql - agrupe por en rangos para incluir rangos sin valores

Question

Suponga un escenario similar a este question. Quiero obtener los siguientes resultados:

score range | number of occurrences 
------------------------------------- 
    0-9  |  11 
    10-19  |  14 
    20-29  |   3 
    ...  |  ... 

Y puedo usar la respuesta seleccionada como una solución:

select t.range as [score range], count(*) as [number of occurences] 
from (
    select case 
    when score between 0 and 9 then ' 0- 9' 
    when score between 10 and 19 then '10-19' 
    else '20-99' end as range 
    from scores) t 
group by t.range 

¿Cómo puedo asegurar que el rango de puntuación de 30-39 será la pantalla incluso cuando no hay resultados en ese rango?

Answer 1

Intentar esta consulta (también en SQL Fiddle):

WITH ranges AS (
    SELECT (ten*10)::text||'-'||(ten*10+9)::text AS range, 
      ten*10 AS r_min, ten*10+9 AS r_max 
     FROM generate_series(0,9) AS t(ten)) 
SELECT r.range, count(s.*) 
    FROM ranges r 
    LEFT JOIN scores s ON s.score BETWEEN r.r_min AND r.r_max 
GROUP BY r.range 
ORDER BY r.range; 

---

EDIT:

Puede ajustar fácilmente el rango cambiando los parámetros a generate_series(). Es posible utilizar la construcción siguiente para asegurarse de que siempre habrá ranges cubrir sus puntuaciones:

SELECT (ten*10)::text||'-'||(ten*10+9)::text AS range, 
     ten*10 AS r_min, ten*10+9 AS r_max 
    FROM generate_series(0,(SELECT max(score)/10 FROM scores)) AS t(ten)) 

para la ranges CTE.

Answer 2

No se puede así, pero si se agrega tabla derivada con rangos cosas llegar a ser posible:

select ranges.range, count(scores.score) as [number of occurences] 
    from 
    (
    select 0 minRange, 9 maxRange, '0-9' range 
    union all 
    select 10, 19, '10-19' 
    union all 
    select 20, 29, '20-29' 
) ranges 
    left join scores 
    on scores.score between ranges.minRange and ranges.maxRange 
group by ranges.range 

No está seguro acerca de la sintaxis de PostgreSQL sin embargo.

EDIT: tiene el derecho de sintaxis:

select ranges."range", count(scores.score) as "number of occurences" 
    from 
    (
    select 0 minRange, 9 maxRange, '0-9' "range" 
    union all 
    select 10, 19, '10-19' 
    union all 
    select 20, 29, '20-29' 
) as ranges 
    left join scores 
    on scores.score between ranges.minRange and ranges.maxRange 
group by ranges.range 

Answer 3

select r.range as [score range], count(*) as [number of occurences] 
from 
    (
    select ' 0- 9' as range, 9 as endrange 
    union all select '10-19',19 
    union all select '20-29',29 
    union all select '30-39',39 
    union all select '40-49',49 
    union all select '50-59',59 
    union all select '60-69',69 
    union all select '70-79',79 
    union all select '80-89',89 
    union all select '90-99',99 
    ) as r 
left join scores s on 
    r.endrange = case 
    when s.score > 90 then 99 
    when s.score > 80 then 89 
    when s.score > 70 then 79 
    when s.score > 60 then 69 
    when s.score > 50 then 59 
    when s.score > 40 then 49 
    when s.score > 30 then 39 
    when s.score > 20 then 29 
    when s.score > 10 then 19 
    when s.score > 0 then 9 
    end 
group by r.range 

Answer 4

En realidad, la solución más simple es esto (por números de 2 dígitos):

select substr(rssi::text, 0, 2) || '0-' || substr(rssi::text, 0, 2) || '9' as range, count(*) 
from sensor_stations 
group by substr(rssi::text, 0, 2) 
order by count(*) desc; 

La salida será algo como esto:

range | count 
-------+------- 
10-19 | 3414 
30-39 | 1363 
20-29 | 1269 
40-49 | 769 
50-59 | 294 
60-69 | 106 
70-79 |  5 
(7 rows) 

No