No data found in sql

Question

ok this has to be simple but I'm getting stuck
I'm trying to display a value when no data is found in a sql querry. similiar to an nvl
but nvl doesn't work because no rows are found.
I don't want to do any pl/sql or user defined functions.
so for example
select nvl(to_char(level), 'no_data_found') lvl
from dual
where 1 = 1
connect by level < 6
returns 1 through 6 as expected
but I am trying to get the following statement to return the words no data found
select nvl(to_char(level), 'no_data_found') lvl
from dual
where 1 <> 1
connect by level < 6
I've been messing with some of the group functions but I can't quite get it.
I thought something like this might be on the right track.
select case count(*) over() when 0 then 'no_data_found' else to_char(level) end lvl
from dual
where 1 <> 1
connect by level < 6

Answer 1

Hi,
Do a UNION ALL of your real query and your default message, but make sure the default message doesn't produce anything when the real query does.
For example:
WITH     real_query     AS
     SELECT  TO_CHAR (LEVEL)     AS lvl
     FROM     dual
     WHERE      1 != 1
     CONNECT BY   LEVEL < 6
SELECT     lvl
FROM     real_query
    UNION ALL
SELECT     'No data found'
FROM     dual
WHERE     NOT EXISTS ( SELECT  1
                   FROM    real_query
;This site normally doesn't display the &lt;&gt; operator, even inside tags.
Always use the other inequality operator, !=, when posting on this site.