MySQL 8.0

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CREATE TABLE mytable(
  date1 VARCHAR(255),
  date2 DATE);

INSERT INTO mytable VALUES
  ('20/11/2022','2022-11-21');

SELECT date1,
       STR_TO_DATE(date1, '%d/%m/%Y'),
       date2,
       DATE_FORMAT(date2, '%d/%m/%Y')
FROM mytable;

date1
STR_TO_DATE(date1, '%d/%m/%Y')
date2
DATE_FORMAT(date2, '%d/%m/%Y')

20/11/2022
2022-11-20
2022-11-21
21/11/2022

ALTER TABLE mytable ADD COLUMN my_date VARCHAR(255);
UPDATE mytable SET my_date=DATE_FORMAT(date2 , '%d/%m/%Y');

SHOW CREATE TABLE mytable;

SELECT * FROM mytable;

Records: 0  Duplicates: 0  Warnings: 0

Rows matched: 1  Changed: 1  Warnings: 0

Table
Create Table

mytable
CREATE TABLE `mytable` (
  `date1` varchar(255) DEFAULT NULL,
  `date2` date DEFAULT NULL,
  `my_date` varchar(255) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci

date1
date2
my_date

20/11/2022
2022-11-21
21/11/2022

SELECT date2,
       DAY(date2),
       my_date,
       DAY(STR_TO_DATE(my_date, '%d/%m/%Y'))
FROM mytable;

date2
DAY(date2)
my_date
DAY(STR_TO_DATE(my_date, '%d/%m/%Y'))

2022-11-21
21
21/11/2022
21

ALTER TABLE mytable MODIFY COLUMN date2 VARCHAR(255);
UPDATE mytable SET date2=DATE_FORMAT(date2, '%d/%m/%Y');

SHOW CREATE TABLE mytable;

SELECT * FROM mytable;

Records: 1  Duplicates: 0  Warnings: 0

Rows matched: 1  Changed: 1  Warnings: 0

Table
Create Table

mytable
CREATE TABLE `mytable` (
  `date1` varchar(255) DEFAULT NULL,
  `date2` varchar(255) DEFAULT NULL,
  `my_date` varchar(255) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci

date1
date2
my_date

20/11/2022
21/11/2022
21/11/2022