By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
CREATE TABLE tablename (date TEXT);
✓
INSERT INTO tablename VALUES
('5/24/2023'), ('12/5/2023'), ('1/1/2023'), ('12/31/2023');
✓
SELECT * FROM tablename;
| date |
|---|
| 5/24/2023 |
| 12/5/2023 |
| 1/1/2023 |
| 12/31/2023 |
UPDATE tablename
SET date = SUBSTR(date, -4) || '-' ||
printf('%02d', date + 0) || '-' ||
printf('%02d', SUBSTR(date, INSTR(date, '/') + 1) + 0);
✓
SELECT * FROM tablename;
| date |
|---|
| 2023-05-24 |
| 2023-12-05 |
| 2023-01-01 |
| 2023-12-31 |