SELECT '|' || dummy || '|' || 'Hello' || '|' FROM DUAL

SELECT '|' || dummy || '|' FROM DUAL

SELECT '|' || 'Hello' || '|' FROM DUAL

CREATE TABLE mytemp
(  
  AVARCHAR       VARCHAR2(10 CHAR),
  ANUMBER        NUMBER(2)
);

-- This works:
INSERT INTO mytemp ( 
SELECT
'Hello' aVARCHAR,
LENGTH('HELLO') aNUMBER
FROM DUAL
);

-- This doesn't work:
-- First the select statement
SELECT
'Hello' aVARCHAR,
LENGTH('HELLO') aNUMBER
FROM DUAL;
-- The result:
'Hello                           ', 5
-- Second insert
INSERT INTO mytemp VALUES ( 'Hello                           ', 5 );

-- Doing an export of the SELECT, and than import the export won't work, because the 'Hello                           '-string is too long.