ALTER TABLE tableName ADD COLUMN (dateCreated TIMESTAMP DEFAULT CURRENT_TIMESTAMP);

ALTER TABLE tabelName ADD COLUMN visible BOOL AFTER id;

ALTER TABLE tableName MODIFY username VARCHAR(255) NOT NULL;

ALTER TABLE tableName ADD created_date TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP AFTER id, ADD modified_date TIMESTAMP on update CURRENT_TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP AFTER created_date;

INSERT INTO tableName (id, name, visible) VALUES ('##', 'data', '1');

UPDATE TABLE tableName SET name='data' WHERE id='##';