with testtab as (select 'Fail' "STAT1", '1' "STAT2" from dual
union all select 'Fail', null from dual
union all select '1', null from dual
union all select null, '2' from dual
union all select '2', '2' from dual
union all select '2', 'FAIL' from dual
union all select null, null from dual)
select * from testtab
where nvl(STAT1,-1) != nvl(STAT2,-1);
возвращает
Stat1 Stat2
Fail 1
Fail null
1 null
null 2
2 FAIL
Stat1 = status_1 в вашем примере.
nvl(value, altValue)
возвращает altValue
, если value
равно нулю