ROUND function

SELECT ROUND (SYSDATE, 'YEAR') "As of day" FROM DUAL

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1/1/2022

SELECT ROUND (TO_DATE ('12-mar-2021'), 'YEAR') "Current Year" FROM DUAL

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1/1/2021

SELECT ROUND (TO_DATE ('12-aug-2021'), 'YEAR') "New Year" FROM DUAL

1/1/2022

First and Last Day of the year

SELECT TRUNC (SYSDATE, 'YEAR') "First Day" FROM DUAL;

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1/1/2021

SELECT ADD_MONTHS (TRUNC (SYSDATE, 'YEAR'), 12) - 1 "Last Day" FROM DUAL;

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12/31/2021

First and last Day of Month

SELECT TRUNC (SYSDATE) - (TO_NUMBER (TO_CHAR (SYSDATE, 'DD')) - 1) FIRST_DAY FROM DUAL;

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10/1/2021

SELECT ADD_MONTHS ( TRUNC (SYSDATE) - (TO_NUMBER (TO_CHAR (SYSDATE, 'DD')) - 1), 1) - 1 LAST_DAY FROM DUAL;

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10/31/2021

SELECT  ADD_MONTHS ( TRUNC (SYSDATE) - (TO_NUMBER (TO_CHAR (SYSDATE, 'DD')) - 1), 1) - 1 LAST_DAY,

        TRUNC(LAST_DAY(ADD_MONTHS(SYSDATE,-1)))+1, TRUNC(LAST_DAY(SYSDATE)) ,

        TRUNC(LAST_DAY(SYSDATE)) LAST_D

FROM DUAL;

10/31/2021    10/1/2021    10/31/2021    10/31/2021