分析関数SUMを組み合わせることができます （現在の合計として使用）およびLAG ：
SQL> WITH data AS (
2 SELECT 'person1' person, 'day1' day, 'Y' flag FROM dual
3 UNION ALL SELECT 'person1' person, 'day2' day, 'Y' flag FROM dual
4 UNION ALL SELECT 'person1' person, 'day3' day, 'Y' flag FROM dual
5 UNION ALL SELECT 'person1' person, 'day4' day, 'N' flag FROM dual
6 UNION ALL SELECT 'person1' person, 'day5' day, 'N' flag FROM dual
7 UNION ALL SELECT 'person1' person, 'day6' day, 'Y' flag FROM dual
8 UNION ALL SELECT 'person1' person, 'day7' day, 'Y' flag FROM dual
9 UNION ALL SELECT 'person1' person, 'day8' day, 'Y' flag FROM dual
10 )
11 SELECT person, DAY, flag, SUM(gap) over (PARTITION BY person
12 ORDER BY DAY) grp
13 FROM (SELECT person, DAY, flag,
14 CASE WHEN flag = lag(flag) over (PARTITION BY person
15 ORDER BY DAY)
16 THEN 0
17 ELSE 1
18 END gap
19 FROM DATA);
PERSON DAY FLAG GRP
------- ---- ---- ----------
person1 day1 Y 1
person1 day2 Y 1
person1 day3 Y 1
person1 day4 N 2
person1 day5 N 2
person1 day6 Y 3
person1 day7 Y 3
person1 day8 Y 3