All Oracle specialists know that a predicate X=NULL can never be true and we should use “X is NULL” in such cases. The Oracle optimizer knows about that, so if we create a table like this:
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ORA exceptions that can’t be caught by exception handler
I know 2 “special” exceptions that can’t be processed in exception handler:
- “ORA-01013: user requested cancel of current operation”
- “ORA-03113: end-of-file on communication channel”
- and + “ORA-00028: your session has been killed” from Matthias Rogel
Tanel Poder described the first one (ORA-01013) in details here: https://tanelpoder.com/2010/02/17/how-to-cancel-a-query-running-in-another-session/ where Tanel shows that this error is based on SIGURG signal (kill -URG):
-- 1013 will not be caught:
declare
e exception;
pragma exception_init(e,-1013);
begin
raise e;
exception when others then dbms_output.put_line('caught');
end;
/
declare
*
ERROR at line 1:
ORA-01013: user requested cancel of current operation
ORA-06512: at line 5
v$blog #funny #friday
select title, short_url
from v$blog
where pubDate>=systimestamp - interval '5' month;
with v$blog as (
select
title
,to_timestamp_tz(pubDate,'DY, dd mon yyyy hh24:mi:ss TZR') pubDate
,short_url
,description
from xmltable(
'/rss/channel/item'
passing
xmltype(httpuritype('https://orasql.org/feed/').getclob())
columns
title varchar2(70) path 'title'
,pubDate varchar2(40) path 'pubDate'
,url varchar2(128) path 'link'
,short_url varchar2(50) path 'guid'
,description varchar2(500) path 'fn:substring(./description,1,500)'
)
)
select title, short_url from v$blog where pubDate>=systimestamp - interval '5' month;
Funny friday Oracle SQL quiz: query running N seconds
Write a pure SQL query with PL/SQL that stop after :N seconds, where :N is a bind variable.
My solution
with v(start_hsecs, delta, flag) as (
select
hsecs as start_hsecs, 0 as delta, 1 as flag
from v$timer
union all
select
v.start_hsecs,
(t.hsecs-v.start_hsecs)/100 as delta,
case when (t.hsecs-v.start_hsecs)/100 > :N /* seconds */ then v.flag*-1 else v.flag+1 end as flag
from v, v$timer t
where v.flag>0 and t.hsecs>=v.start_hsecs
)
select delta
from v
where 0>flag
/
--end
[collapse]
SQL> var N number
SQL> exec :N := 3 /* seconds */;
PL/SQL procedure successfully completed.
SQL> select...
DELTA
----------
3.01
1 row selected.
Elapsed: 00:00:03.01
Another my solution using sys.standard.current_timestamp, so some internal pl/sql…:
select count(*) from dual
connect by sys.standard.current_timestamp - current_timestamp <= interval'3'second;