How do I go from Varchar string into Unix time type? Greenplum - postgresql

Question

I'm fairly inexperienced with SQL let alone PostgreSQL so appreciate your help.
Let's say we have a varchar column called ID that is a combination of IP address and a unix epoch time string.
So when I run this query:
SELECT substring(b.id from char_length (r.IP_address)+2 for 10), b.id, r.ip_address
FROM bq b
INNER JOIN event r ON r.visitor_id::TEXT = b.id::TEXT
LIMIT 3;
Output
substring id ip_address
1460854333 97.128.39.256.1460854333288493 97.128.39.256
So the output of the substring is a unix time stamp but it is in a varchar format. How do I convert the varchar into a unix timestamp? Ultimately I am going to convert that time stamp into date I just don't think I can directly go from the varchar of a unix string to a date?

Answer 1

As Terra said, use the to_timestamp() function:
# select to_timestamp('1460854333') ;
to_timestamp
------------------------
2016-04-16 17:52:13-07
(1 row)
If a date is the type you're after, just add the ::date cast:
# select to_timestamp('1460854333')::date ;
to_timestamp
------------------------
2016-04-16
(1 row)
The function is basically executing this:
select ('epoch'::timestamptz + '1460854333'::float * '1 second'::interval) ;