Get the count of longest streak including the break point - sql

Question

I am working on the problem where I have to get the count of streak with max value, but to get the exact result I have to count that point as well where the streak breaks. My table looks like this
+-----------------+--------+-------+
| customer_number | Months | Flags |
+-----------------+--------+-------+
| 1 | 12 | 1 |
| 1 | 1 | 1 |
| 1 | 2 | 1 |
| 1 | 3 | 1 |
| 1 | 4 | 1 |
| 1 | 5 | 1 |
| 1 | 8 | 1 |
| 1 | 9 | 1 |
| 1 | 10 | 1 |
| 1 | 11 | 1 |
| 6 | 12 | 1 |
| 6 | 1 | 1 |
| 6 | 2 | 1 |
| 6 | 3 | 1 |
| 6 | 4 | 1 |
| 6 | 5 | 4 |
| 6 | 9 | 1 |
| 6 | 10 | 1 |
| 6 | 11 | 1 |
| 7 | 5 | 1 |
| 8 | 9 | 1 |
| 8 | 10 | 1 |
| 8 | 11 | 1 |
| 9 | 9 | 1 |
| 9 | 10 | 1 |
| 9 | 11 | 1 |
| 10 | 11 | 1 |
+-----------------+--------+-------+
and my desired output is
+----------+--------------------+
| Customer | Consecutive streak |
+----------+--------------------+
| 1 | 10 |
| 6 | 6 |
| 7 | 1 |
| 8 | 3 |
| 9 | 3 |
| 10 | 1 |
+----------+--------------------+
the code I have
SELECT customer_number, max(streak) max_consecutive_streak FROM (
SELECT customer_number, COUNT(*) as streak
FROM
(select *,
(row_number() over (order by customer_number) -
row_number() over (order by customer_number)
) as counts
from table1
) cc
group by customer_number, counts
)
GROUP BY 1;
It is working good but for customer_number 6 it returns 5 but I want it to be 6, means it should count 4 as well in its longest streak as the streak breaks at this point. Any idea how can I achieve that?

Answer 1

You can use a cte with row_number:
with cte(r, id, flag) as (
select row_number() over (order by c.customer_number), c.* from customers c
),
freq(id, t, f) as (
select c2.id, c2.f, count(*) from
(select c.id, (select sum(c1.flag!=c.flag) from cte c1 where c1.id=c.id and c1.r <= c.r) f from cte c)
c2 group by c2.id, c2.f
)
select id, max(f) from freq group by id;