MySQL 8.0

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select @@version;


@@version


8.0.30


CREATE TABLE sample (
  Date_Column VARCHAR(25),
  Date_Months_Add INT
)
INSERT INTO sample
VALUES
('26/08/2011', 2),
('25/04/2011', 1),
('16/09/2022', 3),
('14/07/2022', 4);

Records: 4  Duplicates: 0  Warnings: 0


SELECT * FROM sample


Date_Column
Date_Months_Add


26/08/2011
2

25/04/2011
1

16/09/2022
3

14/07/2022
4


SELECT 
  Date_Column, 
  Date_Months_Add, 
  DATE_FORMAT(DATE_ADD(STR_TO_DATE(Date_Column, "%d/%m/%Y" ), INTERVAL Date_Months_Add MONTH), '01/%m/%Y') AS Date_Beginning
FROM sample


Date_Column
Date_Months_Add
Date_Beginning


26/08/2011
2
01/10/2011

25/04/2011
1
01/05/2011

16/09/2022
3
01/12/2022

14/07/2022
4
01/11/2022

Date_Column	Date_Months_Add	Date_Beginning
26/08/2011	2	01/10/2011
25/04/2011	1	01/05/2011
16/09/2022	3	01/12/2022
14/07/2022	4	01/11/2022