WITH T ( YR	, SX )  AS 
(
SELECT 20 ,	'남자' FROM DUAL UNION ALL
SELECT 15	, '여자' FROM DUAL UNION ALL
SELECT 45 ,	'여자' FROM DUAL UNION ALL
SELECT 34 , '남자' FROM DUAL UNION ALL
SELECT 35 ,	'여자' FROM DUAL UNION ALL
SELECT 60 , '남자' FROM DUAL UNION ALL
SELECT 65	, '남자' FROM DUAL 
)

SELECT DECODE(GB,'A','1~10세','B','11~20세','C','21~30세','D','31~40세','E','41~50세','F','51~60세','G','61세이상') "나이"
     ,COUNT(CASE WHEN SX = '남자' THEN 1 END) AS "남자" 
     ,COUNT(CASE WHEN SX = '여자' THEN 1 END) AS "여자"
  FROM 
(
SELECT CASE WHEN YR >= 1  AND YR <= 10 THEN 'A' 
            WHEN YR >= 11 AND YR <= 20 THEN 'B' 
            WHEN YR >= 21 AND YR <= 30 THEN 'C' 
            WHEN YR >= 31 AND YR <= 40 THEN 'D' 
            WHEN YR >= 41 AND YR <= 50 THEN 'E' 
            WHEN YR >= 51 AND YR <= 60 THEN 'F' 
            WHEN YR >= 61  THEN 'G' 
        END GB,
        SX
 FROM T
)
GROUP BY GB
ORDER BY GB

WITH t AS
(
SELECT '30'::numeric age, '남자' sex FROM dual
UNION ALL SELECT '20', '남자' FROM dual
UNION ALL SELECT '15', '여자' FROM dual
UNION ALL SELECT '45', '여자' FROM dual
UNION ALL SELECT '34', '남자' FROM dual
UNION ALL SELECT '35', '여자' FROM dual
UNION ALL SELECT '60', '남자' FROM dual
UNION ALL SELECT '65', '남자' FROM dual
UNION ALL SELECT '36', '여자' FROM dual

)

select case when age<11 then '1~10세' 
        when age<21 then '11~20세'
        when age<31 then '21~30세'
        when age<41 then '31~40세'
        when age<51 then '41~50세'
        when age<61 then '51~60세'
       else '61세 이상' end 나이 ,
       count(case when sex='남자'  then 1 end) as 남자,
       count(case when sex='여자'  then 1 end) as 여자
 from t
 group by 나이
 order by 나이;

WITH T AS(
SELECT 20 age, '남자' gen FROM DUAL UNION ALL 
SELECT 15 age, '여자' gen FROM DUAL UNION ALL 
SELECT 45 age, '여자' gen FROM DUAL UNION ALL 
SELECT 34 age, '남자' gen FROM DUAL UNION ALL 
SELECT 35 age, '여자' gen FROM DUAL UNION ALL 
SELECT 60 age, '남자' gen FROM DUAL UNION ALL 
SELECT 65 age, '남자' gen FROM DUAL UNION ALL 
SELECT 74 age, '남자' gen FROM DUAL 
)

SELECT CASE age_t WHEN 1 THEN '1~10세'
                  WHEN 2 THEN '21~30세'
                  WHEN 3 THEN '31~40세'
                  WHEN 4 THEN '41~50세'
                  WHEN 5 THEN '51~60세'
                  WHEN 6 THEN '61세 이상' END "나이"
      , SUM(DECODE(gen, '남자', 1, 0)) "남자"
      , SUM(DECODE(gen, '여자', 1, 0)) "여자"
FROM 
(
SELECT T.*, CASE WHEN TRUNC((age - 1) / 10) >= 6 THEN 6 ELSE TRUNC((age - 1) / 10) END age_t 
  FROM T
)
GROUP BY age_t
ORDER BY age_t

SELECT DECODE(age_gb, 7, '61세 이상', (age_gb*10-9) ||'~'|| (age_gb*10) ||'세') 나이
     , COUNT(DECODE(gen, '남자', 1)) 남자
     , COUNT(DECODE(gen, '여자', 1)) 여자
  FROM (SELECT age, gen
             , LEAST(CEIL(age/10), 7) age_gb
          FROM t
        )
 GROUP BY age_gb
 ORDER BY age_gb
;

답변주신분들 정말 감사합니다.

하나 배워갑니다.

좋은하루되세요!