dual table postgres doesn't return timestamp

Question

I am trying to select now() from my local postgres database dual table:

select now() from dual;

It returns no rows. Just prints column name now(yyyy-MM-dd HH:mm:ss.ffffff)

What is it that I am missing that it cannot get the system time?

Answer 1

Don't create dual tables

Why are you using a dual table in PostgreSQL to begin with? PostgreSQL has an implicit dual table if there is no from-clause.

SELECT now(); -- works fine.

You can also

SELECT * FROM now(); -- works fine.

• For more information, see my answer to Why does SELECT count(*) return 1?

Creating a dual table should still work

You'll never need a dual table with PostgreSQL, and you shouldn't create one: it just convolutes the syntax. It's also foreign for most PostgreSQL users. That said, it's easy to demonstrate that it works..

test=# CREATE TABLE dual AS ( VALUES (true) );
SELECT 1
test=# SELECT now() FROM dual ;
 now 
-------------------------------
 2017年10月05日 15:34:34.359092-05
(1 row)