Oracle 18c

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
create table DATA_IMPORT (LEARNER_ID number, USER_ID varchar2(30), ERROR_FLAG varchar2(1), IMPORT_NOTIFICATION varchar2(200));
insert into DATA_IMPORT (LEARNER_ID, ERROR_FLAG)
select 1, 'N' from dual
union all
select 2, 'N' from dual
union all
select 2, 'N' from dual
union all
select 3, 'Y' from dual
union all
select null, 'N' from dual
union all
select null, 'N' from dual;
6 rows affected

        SELECT COUNT (D.LEARNER_ID), D.LEARNER_ID
          FROM DATA_IMPORT D
--         WHERE     D.USER_ID IN (SELECT S.OSUSER
--                                   FROM V$SESSION S
--                                  WHERE S.SID IN (SELECT DISTINCT V.SID
--                                                    FROM V$MYSTAT V))
-- sys views not visible here
WHERE 1=1
               AND D.ERROR_FLAG = 'N'
               AND D.LEARNER_ID <> NULL
        HAVING COUNT (D.LEARNER_ID) > 1
      GROUP BY D.LEARNER_ID;
        SELECT COUNT (D.LEARNER_ID), D.LEARNER_ID
          FROM DATA_IMPORT D
--         WHERE     D.USER_ID IN (SELECT S.OSUSER
--                                   FROM V$SESSION S
--                                  WHERE S.SID IN (SELECT DISTINCT V.SID
--                                                    FROM V$MYSTAT V))
-- sys views not visible here
WHERE 1=1
               AND D.ERROR_FLAG = 'N'
               AND D.LEARNER_ID IS NOT NULL
        HAVING COUNT (D.LEARNER_ID) > 1
      GROUP BY D.LEARNER_ID;


COUNT(D.LEARNER_ID)
LEARNER_ID


2
2


        SELECT COUNT (D.LEARNER_ID), D.LEARNER_ID
          FROM DATA_IMPORT D
--         WHERE     D.USER_ID IN (SELECT S.OSUSER
--                                   FROM V$SESSION S
--                                  WHERE S.SID IN (SELECT DISTINCT V.SID
--                                                    FROM V$MYSTAT V))
-- sys views not visible here
WHERE 1=1
               AND D.ERROR_FLAG = 'N'
--               AND D.LEARNER_ID IS NOT NULL
        HAVING COUNT (D.LEARNER_ID) > 1
      GROUP BY D.LEARNER_ID;


COUNT(D.LEARNER_ID)
LEARNER_ID


2
2


        SELECT COUNT (*), D.LEARNER_ID
          FROM DATA_IMPORT D
--         WHERE     D.USER_ID IN (SELECT S.OSUSER
--                                   FROM V$SESSION S
--                                  WHERE S.SID IN (SELECT DISTINCT V.SID
--                                                    FROM V$MYSTAT V))
-- sys views not visible here
WHERE 1=1
               AND D.ERROR_FLAG = 'N'
               AND D.LEARNER_ID IS NOT NULL
        HAVING COUNT (*) > 1
      GROUP BY D.LEARNER_ID;


COUNT(*)
LEARNER_ID


2
2


        SELECT COUNT (*), D.LEARNER_ID
          FROM DATA_IMPORT D
--         WHERE     D.USER_ID IN (SELECT S.OSUSER
--                                   FROM V$SESSION S
--                                  WHERE S.SID IN (SELECT DISTINCT V.SID
--                                                    FROM V$MYSTAT V))
-- sys views not visible here
WHERE 1=1
               AND D.ERROR_FLAG = 'N'
--               AND D.LEARNER_ID IS NOT NULL
        HAVING COUNT (*) > 1
      GROUP BY D.LEARNER_ID;


COUNT(*)
LEARNER_ID


2
null

2
2