Oracle 21c

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ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
CREATE TABLE alphabeta_table ("FILE", NAME, ITEM, "DATE") AS
SELECT 'Alpha1', 'John', 'Apple',  DATE '2024-01-20' FROM DUAL UNION ALL
SELECT 'Alpha1', 'Jane', 'Orange', DATE '2024-01-20' FROM DUAL UNION ALL
SELECT 'Beta2',  'John', 'Apple',  DATE '2024-01-20' FROM DUAL UNION ALL
SELECT 'Beta2',  'Jane', 'Orange', DATE '2024-01-20' FROM DUAL UNION ALL
SELECT 'Alpha2', 'John', 'Apple',  DATE '2024-02-20' FROM DUAL UNION ALL
SELECT 'Alpha2', 'Jane', 'Grape',  DATE '2024-02-20' FROM DUAL;
6 rows affected

SELECT "FILE",
       name,
       item,
       "DATE",
       CASE ROW_NUMBER() OVER (
              PARTITION BY name, item, TRUNC("DATE", 'MM')
              ORDER BY "DATE" ASC
            )
       WHEN 1
       THEN 'Y'
       ELSE 'N'
       END as is_first
FROM   alphabeta_table
ORDER BY
       name,
       item,
       "DATE";


FILE
NAME
ITEM
DATE
IS_FIRST


Alpha2
Jane
Grape
2024-02-20 00:00:00
Y

Beta2
Jane
Orange
2024-01-20 00:00:00
Y

Alpha1
Jane
Orange
2024-01-20 00:00:00
N

Alpha1
John
Apple
2024-01-20 00:00:00
Y

Beta2
John
Apple
2024-01-20 00:00:00
N

Alpha2
John
Apple
2024-02-20 00:00:00
Y

FILE	NAME	ITEM	DATE	IS_FIRST
Alpha2	Jane	Grape	2024-02-20 00:00:00	Y
Beta2	Jane	Orange	2024-01-20 00:00:00	Y
Alpha1	Jane	Orange	2024-01-20 00:00:00	N
Alpha1	John	Apple	2024-01-20 00:00:00	Y
Beta2	John	Apple	2024-01-20 00:00:00	N
Alpha2	John	Apple	2024-02-20 00:00:00	Y