with t as (
            select  account_id,
                    1 tbl_flag
              from  ept01
           union all
            select  account_id,
                    2 tbl_flag
              from  ept02
           union all
            select  account_id,
                    4 tbl_flag
              from  ept03
          )
select  case sum(tbl_flag)
          when 1 then 'Account is missing in ept02 and ept03'
          when 2 then 'Account is missing in ept01 and ept03'
          when 4 then 'Account is missing in ept01 and ept02'
          when 3 then 'Account is missing in ept 03'
          when 5 then 'Account is missing in ept 02'
          when 6 then 'Account is missing in ept 01'
        end missing_accounts
  from  t
  group by account_id
  having sum(tbl_flag) != 7
/

create or replace
  type str_list
    as
      table of varchar2(4000)
/

with t as (
            select  account_id,
                    cast('EPT01' as varchar2(4000)) tbl
              from  ept01
           union all
            select  account_id,
                    'EPT02' tbl
              from  ept02
           union all
            select  account_id,
                    'EPT03' tbl
              from  ept03
           ...
           union all
            select  account_id,
                    'EPT08' tbl
              from  ept08
          )
select  account_id,
        str_list('EPT01','EPT02','EPT03',...'EPT08') multiset except cast(collect(tbl) as str_list) account_id_is_missing_in
  from  t
  group by account_id
  having str_list('EPT01','EPT02','EPT03',...'EPT08') multiset except cast(collect(tbl) as str_list) != str_list()
/

with t as (
            select  job,
                    cast('deptno 10' as varchar2(4000)) d
              from  emp
              where deptno = 10
           union all
            select  job,
                    'deptno 20' d
              from  emp
              where deptno = 20
           union all
            select  job,
                    'deptno 30' d
              from  emp
              where deptno = 30
          )
select  job,
        str_list('deptno 10','deptno 20','deptno 30') multiset except cast(collect(d) as str_list) job_is_missing_in
  from  t
  group by job
  having str_list('deptno 10','deptno 20','deptno 30') multiset except cast(collect(d) as str_list) != str_list()
/

JOB       JOB_IS_MISSING_IN
--------- ----------------------------------------
ANALYST   STR_LIST('deptno 10', 'deptno 30')
PRESIDENT STR_LIST('deptno 20', 'deptno 30')
SALESMAN  STR_LIST('deptno 10', 'deptno 20')

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