Oracle 18c

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ALTER SESSION SET NLS_TERRITORY='America';
SELECT TO_CHAR(DATE '2022-12-11', 'D') AS day, -- a sunday
       (SELECT value FROM NLS_SESSION_PARAMETERS WHERE parameter = 'NLS_TERRITORY')
         AS territory
FROM   DUAL;


DAY
TERRITORY


1
AMERICA


ALTER SESSION SET NLS_TERRITORY='Germany';
SELECT TO_CHAR(DATE '2022-12-11', 'D') AS day, -- a sunday
       (SELECT value FROM NLS_SESSION_PARAMETERS WHERE parameter = 'NLS_TERRITORY')
         AS territory
FROM   DUAL;


DAY
TERRITORY


7
GERMANY


ALTER SESSION SET NLS_TERRITORY='India';
SELECT TO_CHAR(DATE '2022-12-11', 'D') AS day, -- a sunday
       (SELECT value FROM NLS_SESSION_PARAMETERS WHERE parameter = 'NLS_TERRITORY')
         AS territory
FROM   DUAL;


DAY
TERRITORY


1
INDIA


ALTER SESSION SET NLS_TERRITORY='Oman';
SELECT TO_CHAR(DATE '2022-12-11', 'D') AS day, -- a sunday
       (SELECT value FROM NLS_SESSION_PARAMETERS WHERE parameter = 'NLS_TERRITORY')
         AS territory
FROM   DUAL;


DAY
TERRITORY


2
OMAN


ALTER SESSION SET NLS_TERRITORY='Bangladesh';
SELECT TO_CHAR(DATE '2022-12-11', 'D') AS day, -- a sunday
       (SELECT value FROM NLS_SESSION_PARAMETERS WHERE parameter = 'NLS_TERRITORY')
         AS territory
FROM   DUAL;


DAY
TERRITORY


3
BANGLADESH


SELECT TRUNC(SYSDATE + 1) - TRUNC(SYSDATE + 1, 'IW') + 1 AS day
FROM   DUAL;


DAY


6