Find missing number from a sequence for each value in hive

Question

I have a table like below-

User-id  |  sequence
1   0
1   1
1   2
2   1
3   2

here 0 1 and 2 are fixed sequence which a user can at max have, now i want a flag as N where any sequence is missing for a user else flag should be Y.I can say output should like-

1   0  Y
1   1  Y
1   2  Y
2   0  N
2   1  Y
2   2  N
3   0  N
3   1  N
3   2  Y

Answer 1

Select distinct user_id, cross join with sequence (0, 1, 2) to get all user+sequnce combinations, left join with your table to calculate the flag

select us.user_id, 
       us.sequence,
       case when t.user_id is null then 'N' else 'Y' end flag
from
  (--all user sequence combinations
   select u.user_id, s.sequence
     from (select distinct user_id from mytable) u 
          cross join (select stack (3, 0, 1, 2) as sequence) s
  ) us --all user+sequence         
  left join mytable t on us.sequence=t.sequence and us.user_id=t.user_id
 order by us.user_id, us.sequence;

Demo with your data example:

with 
mytable as ( --use your table instead of this
select stack(5,
1, 0,
1, 1,
1, 2,
2, 1,
3, 2) as  (user_id,sequence)
)

select us.user_id, 
       us.sequence,
       case when t.user_id is null then 'N' else 'Y' end flag
from
(--all user sequence combinations
select u.user_id,
       s.sequence
  from (select distinct user_id from mytable) u 
       cross join (select stack (3, 0, 1, 2) as sequence) s
) us --all user+sequence         
 left join mytable t on us.sequence=t.sequence and us.user_id=t.user_id
  order by us.user_id, us.sequence;

Result:

user_id sequence flag
1   0   Y
1   1   Y
1   2   Y
2   0   N
2   1   Y
2   2   N
3   0   N
3   1   N
3   2   Y