Oracleの場合の文字列の比較

空の文字列に対して文字列をチェックしているため、問題が発生しています。 Oracleでは、文字列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

Oracleが空の文字列とnullを処理する方法については、ここもっと何かを見つけます

例：

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

与える：

'' = ''           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

つまり、NULLについて話すときに、信頼できる唯一のチェックです。、is：IS [NOT] NULL