sql - grupper efter i intervaller for at inkludere intervaller uden værdier

Prøv denne forespørgsel (også på 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:

Du kan nemt justere området ved at ændre parametre til generate_series() . Det er muligt at bruge følgende konstruktion for at sikre ranges vil altid dække dine scores:

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))

for ranges CTE.