I write a SQL for query MAX(sample_time) and MIN(sample_time) in the v$active_session_history.
But why bind variables I have defined don't print result ? The following is my operation steps,
set linesize 200 pagesize 200
set verify off
col min(sample_time) for a30
col max(sample_time) for a30
col oldest_sample for a30
col latest_sample for a30
variable oldest_sample varchar2(30);
variable latest_sample varchar2(30);
select min(sample_time), max(sample_time)
into :oldest_sample, :latest_sample
from v$active_session_history;
print :oldest_sample;
print :latest_sample;
/
SQL> set linesize 200 pagesize 200
SQL> set verify off
SQL>
SQL> col min(sample_time) for a30
SQL> col max(sample_time) for a30
SQL>
SQL> col oldest_sample for a30
SQL> col latest_sample for a30
SQL>
SQL> variable oldest_sample varchar2(30);
SQL> variable latest_sample varchar2(30);
SQL>
SQL> select min(sample_time), max(sample_time)
2 into :oldest_sample, :latest_sample
3 from v$active_session_history;
print :oldest_sample;
print :latest_sample;
MIN(SAMPLE_TIME) MAX(SAMPLE_TIME)
------------------------------ ------------------------------
23-APR-18 04.22.28.784 PM 28-APR-18 12.03.33.343 PM
SQL>
OLDEST_SAMPLE
------------------------------
SQL>
LATEST_SAMPLE
------------------------------
Please give me some advice, thanks a lot.