Jämför String i Oracle Case When

Du kontrollerar strängar mot en tom sträng och har därför problem; i Oracle bör du kontrollera om din sträng is not null :

SELECT CASE WHEN '7C54D3E133830A78E040A8C010014B7D' is not null
            THEN '7C54D3E133830A78E040A8C010014B7D'
            WHEN 'e84a4433966c4b8996ce34905acff63d' is not null
            THEN 'e84a4433966c4b8996ce34905acff63d'
            WHEN '7faa9126b1c6412fa58375ab2b2be1db' is not null
            THEN '7faa9126b1c6412fa58375ab2b2be1db'
            ELSE NULL
 END
 FROM DUAL 

Om hur Oracle behandlar tom sträng och null, här du hittar något mer

Ett exempel:

select q'['' = '']'         , case when '' = ''            then 'YES' else 'NO' end from dual union all
select q'['' is null]'      , case when '' is null         then 'YES' else 'NO' end from dual union all 
select q'['' = null ]'      , case when '' = null          then 'YES' else 'NO' end from dual union all 
select q'[null = null]'     , case when null = null        then 'YES' else 'NO' end from dual union all 
select q'[null is null]'    , case when null is null       then 'YES' else 'NO' end from dual union all 
select q'['' != '']'        , case when '' != ''           then 'YES' else 'NO' end from dual union all
select q'['' is not null]'  , case when '' is not null     then 'YES' else 'NO' end from dual union all
select q'['' != null ]'     , case when '' != null         then 'YES' else 'NO' end from dual union all
select q'[null != null]'    , case when null != null       then 'YES' else 'NO' end from dual union all
select q'[null is not null]', case when null is not null   then 'YES' else 'NO' end from dual

ger:

'' = ''           NO
'' is null        YES
'' = null         NO
null = null       NO
null is null      YES
'' != ''          NO
'' is not null    NO
'' != null        NO
null != null      NO
null is not null  NO

Med ett ord, den enda checken du kan lita på när du talar om NULL , är:IS [NOT] NULL