MySQL 8.0

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-- Insert '2021-04-30 08:51:30' using different input formats

CREATE TABLE test ( id INT AUTO_INCREMENT PRIMARY KEY, dt DATETIME);

-- classic string representation

INSERT INTO test (dt) VALUES ('2021-04-30 08:51:30');

-- classic string representation, no leading zeros

INSERT INTO test (dt) VALUES ('2021-4-30 8:51:30');

-- solid string representation

INSERT INTO test (dt) VALUES ('20210430085130');

-- numeric representation

INSERT INTO test (dt) VALUES (20210430085130);

-- custom string representation,

-- according function and specific pattern applied

INSERT INTO test (dt) VALUES (STR_TO_DATE('30.4.2021,8-51-30', '%e\.%c\.%Y,%k-%i-%s'));

SELECT * FROM test;