Compare month in timestamp - oracle

Question

I have a table with TIMESTAMP datatype and I need to compare month value to select all table values. Example the created is the field and wanted to get all the rows which is created between November & December of any year. Tried with below query and it don't work.
select * from table_name where TO_CHAR(created_time, 'mon') in ('nov','dec')

Answer 1

Use EXTRACT:
SELECT *
FROM table_name
WHERE EXTRACT( MONTH from created_time ) IN ( 11, 12 )
Or, you can use TO_CHAR( created_time, 'MM' ) to get the numeric month value (and not worry about language settings as you would have to with the MON format model):
SELECT *
FROM table_name
WHERE TO_CHAR( created_time, 'MM' ) IN ( '11', '12' )
db<>fiddle

Answer 2

Well, there are several ways to achieve this.
1.Using the nlsparam of to_char function
The 'nlsparam' argument specifies the language in which month and day names and abbreviations are returned.
Example
SQL> create table t ( c1 timestamp ) ;
Table created.
SQL> alter session set nls_timestamp_format = 'dd.mm.yyyy hh24:mi:ss.rr' ;
Session altered.
SQL> insert into t values ( systimestamp - 30 ) ;
1 row created.
SQL> insert into t values ( systimestamp ) ;
1 row created.
SQL> select * from t ;
C1
---------------------------------------------------------------------------
30.07.2020 09:29:35.20
29.08.2020 09:29:42.20
SQL> select value from nls_database_parameters where parameter='NLS_LANGUAGE' ;
VALUE
--------------------------------------------------------------------------------
AMERICAN
SQL> select c1 , to_char(c1, 'mon' , 'NLS_DATE_LANGUAGE = american') as mon from t ;
C1
---------------------------------------------------------------------------
MON
------------
30.07.2020 09:29:35
jul
29.08.2020 09:29:42
aug
2.However, to avoid depending in the language, you can use extract and compare the number of the month which is the same in any language. In this case you need to convert the timestamp to a date, but before you need to set the nls_timestamp_format to the specific format.
SQL> alter session set nls_timestamp_format = 'dd.mm.yyyy hh24:mi:ss';
Session altered.
SQL> select c1 , extract(month from to_date(c1,'dd.mm.yyyy hh24:mi:ss')) from t ;
C1
---------------------------------------------------------------------------
EXTRACT(MONTHFROMTO_DATE(C1,'DD.MM.YYYYHH24:MI:SS'))
----------------------------------------------------
30.07.2020 09:29:35
7
29.08.2020 09:29:42
8