Oracle 11g Release 2

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create table client_table(age) as
select 14 from dual
union all select 36 from dual
union all select 37 from dual
union all select 63 from dual
union all select 97 from dual
union all select 98 from dual
union all select 99 from dual;
7 rows affected

SELECT COUNT(*),
      (CASE
        WHEN "CLIENT_TABLE"."AGE" < 18 THEN 'Under 18'
        WHEN "CLIENT_TABLE"."AGE" <= 21 THEN '18 - 21'
        WHEN "CLIENT_TABLE"."AGE" <= 35 THEN '22 - 35'
        WHEN "CLIENT_TABLE"."AGE" <= 50 THEN '36 - 50'
        WHEN "CLIENT_TABLE"."AGE" <= 64 THEN '51 - 64'
        WHEN "CLIENT_TABLE"."AGE" >= 65 THEN '65+'
       END) AS AgeRange
FROM "CLIENT_TABLE"
GROUP BY (CASE
        WHEN "CLIENT_TABLE"."AGE" < 18 THEN 'Under 18'
        WHEN "CLIENT_TABLE"."AGE" <= 21 THEN '18 - 21'
        WHEN "CLIENT_TABLE"."AGE" <= 35 THEN '22 - 35'
        WHEN "CLIENT_TABLE"."AGE" <= 50 THEN '36 - 50'
        WHEN "CLIENT_TABLE"."AGE" <= 64 THEN '51 - 64'
        WHEN "CLIENT_TABLE"."AGE" >= 65 THEN '65+'
       END)
--ORDER BY "CLIENT_TABLE"."AGE"
ORDER BY MIN("CLIENT_TABLE"."AGE")


COUNT(*)
AGERANGE


1
Under 18

2
36 - 50

1
51 - 64

3
65+


WITH "RANGES" ("MIN_AGE", "MAX_AGE", "LABEL") AS (
  SELECT 0, 17, 'Under 18' FROM "DUAL"
  UNION ALL
  SELECT 18, 21, '18 - 21' FROM "DUAL"
  UNION ALL
  SELECT 22, 35, '22 - 35' FROM "DUAL"
  UNION ALL
  SELECT 36, 50, '36 - 50' FROM "DUAL"
  UNION ALL
  SELECT 51, 64, '51 - 64' FROM "DUAL"
  UNION ALL
  SELECT 65, NULL, '65+' FROM "DUAL"
)
SELECT COUNT("CLIENT_TABLE"."AGE"),
       "RANGES"."LABEL" AS AgeRange
FROM "RANGES"
LEFT JOIN "CLIENT_TABLE"
ON "CLIENT_TABLE"."AGE" >= "RANGES"."MIN_AGE"
AND ("RANGES"."MAX_AGE" IS NULL OR "CLIENT_TABLE"."AGE" <= "RANGES"."MAX_AGE")
GROUP BY "RANGES"."MIN_AGE", "RANGES"."LABEL"
ORDER BY "RANGES"."MIN_AGE"


COUNT("CLIENT_TABLE"."AGE")
AGERANGE


1
Under 18

0
18 - 21

0
22 - 35

2
36 - 50

1
51 - 64

3
65+