Postgres 10

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create table my_table (id int)
insert into my_table values (1), (2);
2 rows affected

ALTER TABLE my_table ADD creation_date timestamp
UPDATE my_table  SET creation_date = TO_TIMESTAMP('2019-09-20 13:59', 'YYYY-MM-DD HH24:MI')
2 rows affected

select * from my_table


id
creation_date


1
2019-09-20 13:59:00

2
2019-09-20 13:59:00