TO_TIMESTAMP(‘20151206 00:00:00’, ‘yyyymmdd hh:mm:ss’)
It is wrong in two ways:
1. Incorrect format code
You have repeated the MM format mask twice. MM is month and MI is minutes.
SQL> SELECT TO_TIMESTAMP('20151206 00:00:00', 'yyyymmdd hh:mm:ss') FROM dual;
SELECT TO_TIMESTAMP('20151206 00:00:00', 'yyyymmdd hh:mm:ss') FROM dual
*
ERROR at line 1:
ORA-01810: format code appears twice
2. Incorrect time portion
00:00:00 is wrong as it would throw ORA-01849 since the hour cannot be zero, it must be between 1 and 12.
SQL> SELECT TO_TIMESTAMP('20151206 00:00:00', 'yyyymmdd hh:mi:ss') FROM dual;
SELECT TO_TIMESTAMP('20151206 00:00:00', 'yyyymmdd hh:mi:ss') FROM dual
*
ERROR at line 1:
ORA-01849: hour must be between 1 and 12
The correct way is to either use 24 hour format, or leave the time portion which would default to 12 AM.
For example,
24 hour format:
SQL> SELECT TO_TIMESTAMP('20151206 00:00:00', 'yyyymmdd hh24:mi:ss') my_tmstamp FROM dual;
MY_TMSTAMP
---------------------------------------------------------------------------
06-DEC-15 12.00.00.000000000 AM
No time portion:
SQL> SELECT TO_TIMESTAMP('20151206', 'yyyymmdd') my_tmstamp FROM dual;
MY_TMSTAMP
-----------------------------------------------------------------------
06-DEC-15 12.00.00.000000000 AM