sql - Extract date (yyyy/mm/dd) from a timestamp in PostgreSQL

Question

I want to extract just the date part from a timestamp in PostgreSQL.

I need it to be a postgresql DATE type so I can insert it into another table that expects a DATE value.

For example, if I have 2011/05/26 09:00:00, I want 2011/05/26

I tried casting, but I only get 2011:

timestamp:date
cast(timestamp as date)

I tried to_char() with to_date():

SELECT to_date(to_char(timestamp, 'YYYY/MM/DD'), 'YYYY/MM/DD') 
FROM val3 WHERE id=1;

I tried to make it a function:

CREATE OR REPLACE FUNCTION testing() RETURNS void AS '
DECLARE i_date DATE;
BEGIN
    SELECT to_date(to_char(val1, "YYYY/MM/DD"),"YYYY/MM/DD") 
      INTO i_date FROM exampTable WHERE id=1;
    INSERT INTO foo(testd) VALUES (i);
END

What is the best way to extract date (yyyy/mm/dd) from a timestamp in PostgreSQL?

Answer 1

You can cast your timestamp to a date by suffixing it with ::date. Here, in psql, is a timestamp:

# select '2010-01-01 12:00:00'::timestamp;
      timestamp      
---------------------
 2010-01-01 12:00:00

Now we'll cast it to a date:

wconrad=# select '2010-01-01 12:00:00'::timestamp::date;
    date    
------------
 2010-01-01

On the other hand you can use date_trunc function. The difference between them is that the latter returns the same data type like timestamptz keeping your time zone intact (if you need it).

=> select date_trunc('day', now());
       date_trunc
------------------------
 2015-12-15 00:00:00+02
(1 row)