How to do the same in PostgreSQL?

Question

PostgreSQL

Hello. While new to PostgreSQL. Can you tell me how to make such a conversion function?

UNIX_TIMESTAMP(FROM_UNIXTIME(from_at, "%Y-%m-%d 00:00:00")) as date

Given function from MYSQL

Answer 1

If I understand correctly what you are doing and in from_at you have unix, then you need to do the following:

SELECT EXTRACT(EPOCH FROM to_char(to_timestamp(from_at), 'YYYY-MM-DD 00:00:00')::timestamp);

Answer 2

If you need a UNIXTIME for the start of the day, you can use this option:

select extract(epoch from date_trunc('day', to_timestamp(from_at))) as date;

You can experiment with SQL queries here